make.bash: avoid warning when bootstrap doesn't support GOOS/GOARCH

Currently, if make.bash is run with a GOOS or GOARCH that the
bootstrap toolchain doesn't support, it will print an ominous but
harmless warning like:

  2020/09/21 09:05:27 unsupported GOARCH arm64

This comes from the invocation of "go version" to get the exact
bootstrap toolchain version.

Since the GOOS and GOARCH don't matter for this purpose, this CL
simply clears them on the invocation of the bootstrap toolchain's "go
version".

Fixes #41525.

Change-Id: I17d44eaafed9999b9fa7dcb9fb100b5fd5e554d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/256297
Trust: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

diff --git a/src/make.bash b/src/make.bash
index 3a84658c72deabcc2db0435ef09471dc6562060b..b58f27bb1bc6bd661f336d3665c4c4790e3a438f 100755 (executable)
--- a/src/make.bash
+++ b/src/make.bash
@@ -167,7 +167,10 @@ if [ ! -x "$GOROOT_BOOTSTRAP/bin/go" ]; then
        echo "Set \$GOROOT_BOOTSTRAP to a working Go tree >= Go 1.4." >&2
        exit 1
 fi
-GOROOT_BOOTSTRAP_VERSION=$($GOROOT_BOOTSTRAP/bin/go version | sed 's/go version //')
+# Get the exact bootstrap toolchain version to help with debugging.
+# We clear GOOS and GOARCH to avoid an ominous but harmless warning if
+# the bootstrap doesn't support them.
+GOROOT_BOOTSTRAP_VERSION=$(GOOS= GOARCH= $GOROOT_BOOTSTRAP/bin/go version | sed 's/go version //')
 echo "Building Go cmd/dist using $GOROOT_BOOTSTRAP. ($GOROOT_BOOTSTRAP_VERSION)"
 if $verbose; then
        echo cmd/dist