buildgcc: surround *.log with apostrophes when build fails

Apparently the script's output text is unclear.
Emphasize the file name, keeping the dot to close the sentence.

Change-Id: I1f214b71629eda5fc54e5671ce63e58948343656
Signed-off-by: Idwer Vollering <vidwer@gmail.com>
Reviewed-on: https://review.coreboot.org/21012
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Nico Huber <nico.h@gmx.de>

util/crossgcc/buildgcc

@@ -411,7 +411,7 @@ generic_build()
 		if [ ! -f "$builddir/.failed" ]; then
 			touch "$success";
 		else
-			printf "${RED}failed${NC}. Check $builddir/build.log.\n"
+			printf "${RED}failed${NC}. Check '$builddir/build.log'.\n"
 			exit 1
 		fi
 		printf "${green}ok${NC}\n"