Add -fopenmp to cflags in pkgconfig file if set

Makefile.install

@@ -14,6 +14,9 @@ endif
 ifeq ($(INTERFACE64),1)
 USE_64BITINT=1
 endif
+ifeq ($(USE_OPENMP),1)
+	FOMP_OPT:= -fopenmp
+endif
 
 PREFIX ?= /opt/OpenBLAS
 
@@ -178,6 +181,7 @@ endif
 	@echo 'libnamesuffix='$(LIBNAMESUFFIX) >> "$(PKGFILE)"
 	@echo 'libsuffix='$(SYMBOLSUFFIX) >> "$(PKGFILE)"
 	@echo 'includedir='$(OPENBLAS_INCLUDE_DIR) >> "$(PKGFILE)"
+	@echo 'omp_opt='$(FOMP_OPT) >> "$(PKGFILE)"
 	@echo 'openblas_config= USE_64BITINT='$(INTERFACE64) 'DYNAMIC_ARCH='$(DYNAMIC_ARCH) 'DYNAMIC_OLDER='$(DYNAMIC_OLDER) 'NO_CBLAS='$(NO_CBLAS) 'NO_LAPACK='$(NO_LAPACK) 'NO_LAPACKE='$(NO_LAPACKE) 'NO_AFFINITY='$(NO_AFFINITY) 'USE_OPENMP='$(USE_OPENMP) $(TARGET) 'MAX_THREADS='$(NUM_THREADS)>> "$(PKGFILE)"
 	@echo 'version='$(VERSION) >> "$(PKGFILE)"
 	@echo 'extralib='$(PKG_EXTRALIB) >> "$(PKGFILE)"