cmd/link: don't let dsymutil delete our temp directory

To work around #59026, where dsymutil may not clean up its temp
directory at exit, we set DSYMUTIL_REPRODUCER_PATH to our temp
directory so it uses that, and we can delete it at the end.

In Xcode 16 beta, dsymutil deletes the DSYMUTIL_REPRODUCER_PATH
directory even if it is not empty. We still need our tmpdir at the
point, so give a subdirectory to dsymutil instead.

For #68088.

Change-Id: I18759cc39512819bbd0511793ce917eae72245d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/593659
Reviewed-by: Than McIntosh <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

src/cmd/link/internal/ld/lib.go

@@ -2009,7 +2009,15 @@ func (ctxt *Link) hostlink() {
 		cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
 		// dsymutil may not clean up its temp directory at exit.
 		// Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
-		cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+*flagTmpdir)
+		// dsymutil (Apple LLVM version 16.0.0) deletes the directory
+		// even if it is not empty. We still need our tmpdir, so give a
+		// subdirectory to dsymutil.
+		dsymDir := filepath.Join(*flagTmpdir, "dsymutil")
+		err := os.MkdirAll(dsymDir, 0777)
+		if err != nil {
+			Exitf("fail to create temp dir: %v", err)
+		}
+		cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+dsymDir)
 		if ctxt.Debugvlog != 0 {
 			ctxt.Logf("host link dsymutil:")
 			for _, v := range cmd.Args {