internal/testenv: TestHasGoBuild failures on the LUCI noopt builders

[mknyszek]

I fixed this issue on tip (https://go.dev/cl/558596), but forgot to backport the fix.

[mknyszek]

@gopherbot Please open backport issues. This issue should be fixed as it means the LUCI noopt builder consistently fails on release branches. The fix is test-only, so very safe.

[gopherbot]

Backport issue(s) opened: #65471 (for 1.20), #65472 (for 1.21).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/560696 mentions this issue: [release-branch.go1.22] internal/testenv: allow "-noopt" anywhere in builder name in test

[gopherbot]

Change https://go.dev/cl/560518 mentions this issue: [release-branch.go1.21] internal/testenv: allow "-noopt" anywhere in builder name in test