Fixed build (Only PHP above 7.1 could run the gen_stub.php)

Author: laruence

build/Makefile.global

@@ -142,8 +142,15 @@ prof-clean:
 prof-use:
 	CCACHE_DISABLE=1 $(MAKE) PROF_FLAGS=-fprofile-use all
 
+# olny php above 7.1.0 supports nullable return type
 %_arginfo.h: %.stub.php
-	if type php >/dev/null 2>/dev/null; then php $(top_srcdir)/scripts/dev/gen_stub.php $<; fi
+	-@if type php >/dev/null 2>/dev/null; \
+	 then \
+	  if test `php -v | head -n1 | cut -d" " -f 2 | sed "s/$$/\n7.0.99/" | sort -rV | head -n1` != "7.0.99"; \
+	  then \
+	   php $(top_srcdir)/scripts/dev/gen_stub.php $<; \
+	  fi; \
+	 fi;
 
 # As we don't track includes, this is just a heuristic
 %.c: %_arginfo.h