hook up c++ thread test (main makefile)

Makefile

@@ -34,7 +34,7 @@ endif
 
 LAPACK_NOOPT := $(filter-out -O0 -O1 -O2 -O3 -Ofast,$(LAPACK_FFLAGS))
 
-SUBDIRS_ALL = $(SUBDIRS) test ctest utest exports benchmark ../laswp ../bench
+SUBDIRS_ALL = $(SUBDIRS) test ctest utest exports benchmark ../laswp ../bench cpp_thread_test
 
 .PHONY : all libs netlib $(RELA) test ctest shared install
 .NOTPARALLEL : all libs $(RELA) prof lapack-test install blas-test
@@ -127,6 +127,9 @@ ifndef NO_FBLAS
 endif
 ifndef NO_CBLAS
 	$(MAKE) -C ctest all
+ifeq ($(CPP_THREAD_SAFETY_TEST), 1)
+	$(MAKE) -C cpp_thread_test all
+endif
 endif
 endif