Move aarch64-apple-darwin to tier 2

Drive-by fixes to update the naming of "OSX" [sic] to "macOS".

Author: shepmaster

src/doc/rustc/src/platform-support.md

@@ -37,7 +37,7 @@ target | std | host | notes
 `i686-pc-windows-gnu` | ✓ | ✓ | 32-bit MinGW (Windows 7+)
 `i686-pc-windows-msvc` | ✓ | ✓ | 32-bit MSVC (Windows 7+)
 `i686-unknown-linux-gnu` | ✓ | ✓ | 32-bit Linux (kernel 2.6.32+, glibc 2.11+)
-`x86_64-apple-darwin` | ✓ | ✓ | 64-bit OSX (10.7+, Lion+)
+`x86_64-apple-darwin` | ✓ | ✓ | 64-bit macOS (10.7+, Lion+)
 `x86_64-pc-windows-gnu` | ✓ | ✓ | 64-bit MinGW (Windows 7+)
 `x86_64-pc-windows-msvc` | ✓ | ✓ | 64-bit MSVC (Windows 7+)
 `x86_64-unknown-linux-gnu` | ✓ | ✓ | 64-bit Linux (kernel 2.6.32+, glibc 2.11+)
@@ -57,6 +57,7 @@ Specifically, these platforms are required to have each of the following:
 
 target | std | host | notes
 -------|-----|------|-------
+`aarch64-apple-darwin` | ✓ |  | ARM64 macOS (11.0+, Big Sur+)
 `aarch64-apple-ios` | ✓ |  | ARM64 iOS
 `aarch64-fuchsia` | ✓ |  | ARM64 Fuchsia
 `aarch64-linux-android` | ✓ |  | ARM64 Android
@@ -145,7 +146,6 @@ not available.
 
 target | std | host | notes
 -------|-----|------|-------
-`aarch64-apple-darwin` | ? |  | ARM64 macOS
 `aarch64-apple-tvos` | * |  | ARM64 tvOS
 `aarch64-unknown-cloudabi` | ✓ |  | ARM64 CloudABI
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
@@ -168,7 +168,7 @@ target | std | host | notes
 `avr-unknown-gnu-atmega328` | ✗ |  | AVR. Requires `-Z build-std=core`
 `hexagon-unknown-linux-musl` | ? |  |
 `i386-apple-ios` | ✓ |  | 32-bit x86 iOS
-`i686-apple-darwin` | ✓ | ✓ | 32-bit OSX (10.7+, Lion+)
+`i686-apple-darwin` | ✓ | ✓ | 32-bit macOS (10.7+, Lion+)
 `i686-pc-windows-msvc` | ✓ |  | 32-bit Windows XP support
 `i686-unknown-cloudabi` | ✓ |  | 32-bit CloudABI
 `i686-unknown-uefi` | ? |  | 32-bit UEFI