run-make test: using single quotes to not trigger the shell

Author: TimNN

tests/run-make/inaccessible-temp-dir/Makefile

@@ -25,7 +25,7 @@ all:
 	# Run rustc with `-Ztemps-dir` set to a directory 
 	# *inside* the inaccessible one, so that it can't create it
 	$(RUSTC) program.rs -Ztemps-dir=$(TMPDIR)/inaccessible/tmp 2>&1 \
-		| $(CGREP) "failed to find or create the directory specified by `--temps-dir`"
+		| $(CGREP) 'failed to find or create the directory specified by `--temps-dir`'
 
 	# Make the inaccessible directory accessible,
 	# so that compiletest can delete the temp dir