cmd/go/testdata/script: add darwin skips for selected buildrepro tests
Skip two build reproducibility tests (build_issue48319 and
build_plugin_reproducible) on Darwin if GO_BUILDER_NAME is set until
issue 64947 can be resolved; on the LUCI darwin longtest builder the
more contemporary version of Xcode is doing things that are unfriendly
to Go's build reproducibility.
For #64947.
Change-Id: Iebd433ad6dfeb84b6504ae9355231d897d8ae174
Reviewed-on: https://go-review.googlesource.com/c/go/+/565376 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>