src/buildall.bash: mention no longer being used by Go build system

The buildall.bash script was initially added in 2015 (in CL 9438),
documented as used in the implementation of the new compile-only
builders at the time.

That description was updated as the builder implementation changed
from "linux-amd64-compilesmoke" to "all-compile" and most recently
to "misc-compile", which it still mentions today.

The build system stopped using it in CL 464955 and there are no plans
to use it again in the future, so update the description so that it's
not misleading. Notably, adding additional checks to this script does
not mean they will be caught by builders.

Updates #31916.
Updates #58163.

Change-Id: I17558b1c150a3ad95105de14511c51791287991b
Reviewed-on: https://go-review.googlesource.com/c/go/+/513755
Reviewed-by: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

src/buildall.bash

@@ -6,8 +6,12 @@
 # Usage: buildall.bash [-e] [pattern]
 #
 # buildall.bash builds the standard library for all Go-supported
-# architectures. It is used by the "misc-compile" trybot builders,
-# as a smoke test to quickly flag portability issues.
+# architectures.
+#
+# Originally the Go build system used it as a smoke test to quickly
+# flag portability issues in builders named "misc-compile" or "all-compile".
+# As of CL 464955, the build system uses make.bash -compile-only instead,
+# so this script no longer runs in any automated fashion.
 #
 # Options:
 #   -e: stop at first failure

src/cmd/go/internal/work/exec.go

@@ -1250,7 +1250,7 @@ func (b *Builder) vet(ctx context.Context, a *Action) error {
 		// that vet doesn't like in low-level packages
 		// like runtime, sync, and reflect.
 		// Note that $GOROOT/src/buildall.bash
-		// does the same for the misc-compile trybots
+		// does the same
 		// and should be updated if these flags are
 		// changed here.
 		vetFlags = []string{"-unsafeptr=false"}
@@ -1260,7 +1260,7 @@ func (b *Builder) vet(ctx context.Context, a *Action) error {
 		// like hard-coded forced returns or panics that make
 		// code unreachable. It's unreasonable to insist on files
 		// not having any unreachable code during "go test".
-		// (buildall.bash still runs with -unreachable enabled
+		// (buildall.bash still has -unreachable enabled
 		// for the overall whole-tree scan.)
 		if cfg.CmdName == "test" {
 			vetFlags = append(vetFlags, "-unreachable=false")