cmd/internal/testdir: pass -buildid to link command

The new dynamic loader in macOS 26 beta doesn't like binaries
without LC_UUID. Binaries built by "go build" have LC_UUID by
default. When invoking the linker manually, it has an LC_UUID by
default if a Go buildid is specified. This CL makes it pass
-buildid to link command for the test directory, so the binaries
will have LC_UUID.

Change-Id: I9369aeb7323d211eda80e4f22f459c220085f61d
Reviewed-on: https://go-review.googlesource.com/c/go/+/692876
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: cherrymui

src/cmd/internal/testdir/testdir_test.go

@@ -242,7 +242,7 @@ func linkFile(runcmd runCmd, outfile, infile string, importcfg string, ldflags [
 	if strings.HasSuffix(infile, ".go") {
 		infile = infile[:len(infile)-3] + ".o"
 	}
-	cmd := []string{goTool, "tool", "link", "-s", "-w", "-o", outfile, "-importcfg=" + importcfg}
+	cmd := []string{goTool, "tool", "link", "-s", "-w", "-buildid=test", "-o", outfile, "-importcfg=" + importcfg}
 	if *linkshared {
 		cmd = append(cmd, "-linkshared", "-installsuffix=dynlink")
 	}