cmd/dist: skip the staleness check for 'cmd' when testing on aix-ppc64

The gcc toolchain on the aix-ppc64 builder apparently does not achieve
reproducible builds for packages that use cgo, which causes the
binaries in cmd that use package "net" (cmd/go, cmd/pprof, and
cmd/trace) to appear stale whenever the Go build cache is cleared.

For now, we work around the staleness by rebuilding std and simply not
checking whether cmd is stale.

For #56896.
Updates #47257.

Change-Id: I15f86e72dee53904b881710d5d5d613872361510
Reviewed-on: https://go-review.googlesource.com/c/go/+/452680
Run-TryBot: Bryan Mills <[email protected]>
Reviewed-by: Ayappan Perumal <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Russ Cox <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

src/cmd/dist/test.go

@@ -159,7 +159,7 @@ func (t *tester) run() {
 	}
 
 	if !t.listMode {
-		if os.Getenv("GO_BUILDER_NAME") == "" {
+		if builder := os.Getenv("GO_BUILDER_NAME"); builder == "" {
 			// Complete rebuild bootstrap, even with -no-rebuild.
 			// If everything is up-to-date, this is a no-op.
 			// If everything is not up-to-date, the first checkNotStale
@@ -185,7 +185,15 @@ func (t *tester) run() {
 			// running dist test, so rebuild (but don't install) std and cmd to make
 			// sure packages without install targets are cached so they are not stale.
 			goCmd("go", "build", "std", "cmd") // make sure dependencies of targets are cached
-			checkNotStale("go", "std", "cmd")
+			if builder == "aix-ppc64" {
+				// The aix-ppc64 builder for some reason does not have deterministic cgo
+				// builds, so "cmd" is stale. Fortunately, most of the tests don't care.
+				// TODO(#56896): remove this special case once the builder supports
+				// determistic cgo builds.
+				checkNotStale("go", "std")
+			} else {
+				checkNotStale("go", "std", "cmd")
+			}
 		}
 	}