utest: test fork safety on OpenMP >= 5

In addition to testing fork safety on non-OpenMP builds, test it when
omp_pause_resource_all() is available to release the locks.

utest/Makefile

@@ -44,10 +44,14 @@ endif
 #this does not work with OpenMP nor with native Windows or Android threads
 # FIXME TBD if this works on OSX, SunOS, POWER and zarch
 ifeq ($(OSNAME), $(filter $(OSNAME),Linux CYGWIN_NT))
-ifneq ($(USE_OPENMP), 1)
-OBJS += test_fork.o
+ifeq ($(USE_OPENMP), 1)
+ifeq ($(HAVE_OMP_PAUSE_RESOURCE_ALL), 1)
+   OBJS += test_fork.o
 endif
-OBJS += test_post_fork.o
+else
+  OBJS += test_fork.o
+endif
+ OBJS += test_post_fork.o
 endif
 
 ifeq ($(C_COMPILER), PGI)