Don't run tests if build fails in quickcheck.

Makefile

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 337 matching lines @@
 
 native.check: native
         @tools/run-tests.py $(TESTJOBS) --outdir=$(OUTDIR)/native \
             --arch-and-mode=. $(TESTFLAGS)
 
 FASTTESTFLAGS = --flaky-tests=skip --slow-tests=skip --pass-fail-tests=skip \
                 --variants=default,stress
 FASTTESTMODES = ia32.release,x64.release,ia32.debug,x64.debug,arm.debug
 
 quickcheck:
-        @$(MAKE) all optdebug=on; \
-        tools/run-tests.py $(TESTJOBS) --outdir=$(OUTDIR) \
+        @$(MAKE) all optdebug=on
+        @tools/run-tests.py $(TESTJOBS) --outdir=$(OUTDIR) \
             --arch-and-mode=$(FASTTESTMODES) $(FASTTESTFLAGS) $(TESTFLAGS)
 qc: quickcheck
 
 # Clean targets. You can clean each architecture individually, or everything.
 $(addsuffix .clean, $(ARCHES) $(ANDROID_ARCHES) $(NACL_ARCHES)):
         rm -f $(OUTDIR)/Makefile.$(basename $@)
         rm -rf $(OUTDIR)/$(basename $@).release
         rm -rf $(OUTDIR)/$(basename $@).debug
         find $(OUTDIR) -regex '.*\(host\|target\).$(basename $@)\.mk' -delete
 
@@ skipping 58 matching lines @@
         @$(OUTDIR)/ia32.release/d8 --dump-heap-constants >> $(DUMP_FILE)
 
 # Dependencies.
 # Remember to keep these in sync with the DEPS file.
 dependencies:
         svn checkout --force http://gyp.googlecode.com/svn/trunk build/gyp \
             --revision 1685
         svn checkout --force \
             https://src.chromium.org/chrome/trunk/deps/third_party/icu46 \
             third_party/icu --revision 214189