cmd/dist: add GO_TEST_ASMFLAGS to set -asmflags during dist test

If we run into a need for finer control over when -asmflags gets set,
there can be an asmflags field added to goTest, analogously to the
existing gcflags and ldflags fields. Start with a minimal change for
what is currently needed, since not adding something we ourselves don't
use makes it easier to avoid inadvertently ending up maintaining it
because we can't be sure whether someone else started to depend on it.

For #77427.

Change-Id: I5e80874861cadf95fe770af6712b2c3f172c990a
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-spectre
Reviewed-on: https://go-review.googlesource.com/c/go/+/758740
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/run.bash b/src/run.bash
index cb474325c4..e774f03b30 100755
--- a/src/run.bash
+++ b/src/run.bash
@@ -21,6 +21,13 @@
 #
 # GO_TEST_TIMEOUT_SCALE: a non-negative integer factor to scale test timeout by.
 # Defaults to 1.
+#
+# GO_TEST_ASMFLAGS: Additional go tool asm arguments to use when running the tests.
+# This environment variable is an internal implementation detail between the
+# Go build system (x/build) and cmd/dist to enable builders that need to control this,
+# and will be removed if it stops being needed, or if a more general-purpose
+# GO_ASMFLAGS environment variable gets added to make.bash and supersedes this
+# test-only subset of it. See go.dev/issue/77427.
 
 set -e