rollup merge of rust-lang#19983: Munksgaard/fix-19981

The use of `+a+x` is deprecated.

Fixes rust-lang#19981.

Author: alexcrichton

mk/tests.mk

@@ -300,7 +300,7 @@ tidy:
 		| xargs -n 10 $(CFG_PYTHON) $(S)src/etc/tidy.py
 		$(Q)echo $(ALL_HS) \
 		| xargs -n 10 $(CFG_PYTHON) $(S)src/etc/tidy.py
-		$(Q)find $(S)src -type f -perm +a+x \
+		$(Q)find $(S)src -type f -perm /a+x \
 		    -not -name '*.rs' -and -not -name '*.py' \
 		    -and -not -name '*.sh' \
 		| grep '^$(S)src/jemalloc' -v \