cmd/compile: add script testing facility for compiler use
Add support for running script tests as part of the compiler's suite
of tests, hooking in the script test engine packages recently moved
from cmd/go to cmd/internal. These script tests will use the test
binary itself as the compile tool for Go builds, and can also run the
C compiler if needed. New script test cases (*.txt files) should be
added to the directory cmd/compile/testdata/script.
Updates #68606.
Change-Id: I9b056a07024b0a72320a89ad734e4b4a51f1c10c
Reviewed-on: https://go-review.googlesource.com/c/go/+/601361 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>