cmd/link: ignore mapping symbols on riscv64

[ziyao233]

Specified in RISC-V ELF psABI1, mapping symbols are symbols starting
with "$d" or "$x" with STT_NOTYPE, STB_LOCAL and zero sizes, indicating
boundaries between code and data in the same section.

Let's simply ignore them as they're only markers instead of real symbols.
This fixes linking errors like

sym#63 ("$d"): ignoring symbol in section 4 (".riscv.attributes") (type 0)

when using CGO together with Clang and internal linker, which are caused
by unnecessary (but technically correct) mapping symbols created by LLVM
for various sections.

Fixes #73516

[gopherbot]

This PR (HEAD: a22540f) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/669675.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Gopher Robot:

Patch Set 1:

Congratulations on opening your first change. Thank you for your contribution!

Next steps:
A maintainer will review your change and provide feedback. See
https://go.dev/doc/contribute#review for more info and tips to get your
patch through code review.

Most changes in the Go project go through a few rounds of revision. This can be
surprising to people new to the project. The careful, iterative review process
is our way of helping mentor contributors and ensuring that their contributions
have a lasting impact.

During May-July and Nov-Jan the Go project is in a code freeze, during which
little code gets reviewed or merged. If a reviewer responds with a comment like
R=go1.11 or adds a tag like "wait-release", it means that this CL will be
reviewed as part of the next development cycle. See https://go.dev/s/release
for more details.

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Yao Zi:

Patch Set 3:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Julian Zhu:

Patch Set 3: Commit-Queue+1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 3:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2025-05-03T11:17:53Z","revision":"7edef74737d6f258a39416fbe6f58441b6f50664"}

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Julian Zhu:

Patch Set 3: -Commit-Queue

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 3:

This CL has passed the run

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 3: LUCI-TryBot-Result+1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Meng Zhuo:

Patch Set 3:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Yao Zi:

Patch Set 3:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Meng Zhuo:

Patch Set 3: Code-Review+2

(3 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: d7842ce) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/669675.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Yao Zi:

Patch Set 5:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Cherry Mui:

Patch Set 5: Code-Review+2

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Cherry Mui:

Patch Set 5: Commit-Queue+1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 5:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2025-05-09T15:18:36Z","revision":"1c286dd213a1c6bdd81b8502afa8c9b99bccd671"}

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Cherry Mui:

Patch Set 5: -Commit-Queue

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 5:

This CL has passed the run

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 5: LUCI-TryBot-Result+1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Michael Knyszek:

Patch Set 5: Code-Review+1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/669675.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR is being closed because golang.org/cl/669675 has been merged.