This patch disable GC-sensitive tests.  This is particularly useful when
compiling with `-O0' (as is done with coverage analysis) since there may
be many false references held on the stack, leading to the failure of
such tests.

--- a/test-suite/tests/gc.test
+++ b/test-suite/tests/gc.test
@@ -67,6 +67,7 @@
 
 (with-test-prefix "gc"
   (pass-if "Unused modules are removed"
+    (throw 'unresolved)
     (let* ((guard (make-guardian))
            (total 1000))

--- a/test-suite/tests/threads.test
+++ b/test-suite/tests/threads.test
@@ -366,6 +366,7 @@
 	    (not (mutex-owner m))))
 
         (pass-if "mutex with owner not retained (bug #27450)"
+          (throw 'unresolved)
           (let ((g (make-guardian)))
             (g (let ((m (make-mutex))) (lock-mutex m) m))