Improve -valgrind error-handling.

Passing --quiet makes valgrind only print out errors, so we don't need
to suppress things. Combine that with checking valgrind's dedicated exit
code so we notice errors that happen before the "---DONE---" marker.

This makes that marker unnecessary for valgrind. all_tests.go was not
sensitive to this, but still would do well to have valgrind be silent.

Change-Id: I841edf7de87081137e38990e647e989fd7567295
Reviewed-on: https://boringssl-review.googlesource.com/11128
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/util/all_tests.go b/util/all_tests.go
index d361651..a937c8c 100644
--- a/util/all_tests.go
+++ b/util/all_tests.go
@@ -104,7 +104,7 @@
 }
 
 func valgrindOf(dbAttach bool, path string, args ...string) *exec.Cmd {
-	valgrindArgs := []string{"--error-exitcode=99", "--track-origins=yes", "--leak-check=full"}
+	valgrindArgs := []string{"--error-exitcode=99", "--track-origins=yes", "--leak-check=full", "--quiet"}
 	if dbAttach {
 		valgrindArgs = append(valgrindArgs, "--db-attach=yes", "--db-command=xterm -e gdb -nw %f %p")
 	}