all: flaky failures on openbsd/ppc64

[gopherbot]

#!watchflakes
post <- goos == "openbsd" && goarch == "ppc64"

There have been a number of flaky failures on the openbsd/ppc64 builder lately. Many (but not all) are "resource temporarily unavailable".

Example (log):

=== RUN   TestMachOBuildVersion
=== PAUSE TestMachOBuildVersion
=== CONT  TestMachOBuildVersion
    link_test.go:386: [/home/swarming/.swarming/w/ir/x/w/goroot/bin/go build -ldflags=-linkmode=internal -o /home/swarming/.swarming/w/ir/x/t/TestMachOBuildVersion613685595/001/main /home/swarming/.swarming/w/ir/x/t/TestMachOBuildVersion613685595/001/main.go]: exit status 1:
        internal/bytealg: /home/swarming/.swarming/w/ir/x/w/goroot/pkg/tool/openbsd_ppc64/asm: fork/exec /home/swarming/.swarming/w/ir/x/w/goroot/pkg/tool/openbsd_ppc64/asm: resource temporarily unavailable
--- FAIL: TestMachOBuildVersion (15.67s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestMachOBuildVersion"

2025-06-09 17:55 go1.25-openbsd-ppc64 release-branch.go1.25@049a5e60 cmd/link.TestMachOBuildVersion (log)

=== RUN   TestMachOBuildVersion
=== PAUSE TestMachOBuildVersion
=== CONT  TestMachOBuildVersion
    link_test.go:386: [/home/swarming/.swarming/w/ir/x/w/goroot/bin/go build -ldflags=-linkmode=internal -o /home/swarming/.swarming/w/ir/x/t/TestMachOBuildVersion613685595/001/main /home/swarming/.swarming/w/ir/x/t/TestMachOBuildVersion613685595/001/main.go]: exit status 1:
        internal/bytealg: /home/swarming/.swarming/w/ir/x/w/goroot/pkg/tool/openbsd_ppc64/asm: fork/exec /home/swarming/.swarming/w/ir/x/w/goroot/pkg/tool/openbsd_ppc64/asm: resource temporarily unavailable
--- FAIL: TestMachOBuildVersion (15.67s)

— watchflakes

[mknyszek]

CC @golang/openbsd

[mknyszek]

Possibly related to #74173, #74178, #74186, #74126.