build/boot/roms: don't create empty bin/ directory

also: only return zero status if rom images were succesfully
built, and print a list of each rom image directory based on
what was actually compiled, rather than just saying that the
rom images are stored under bin/

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/build/boot/roms_helper

@@ -186,8 +186,6 @@ build_dependencies()
 		./handle make file -b ${memtest_bin%/*} || \
 		    err "cannot build memtest86+"
 
-	[ -d "${romdir}/" ] || mkdir -p "${romdir}/" || \
-	    err "cannot create rom directory: \"${romdir}\""
 	rm -f "${romdir}"/* || err "cannot: rm -f \"${romdir}\"/*"
 
 	build_dependency_grub
@@ -529,6 +527,9 @@ moverom() {
 
 	printf "\nCreating new ROM image: %s\n" "${newrompath}"
 
+	[ -d "${newrompath%/*}" ] || mkdir -p "${newrompath%/*}/" || \
+	    err "moverom: cannot create rom directory: \"${newrompath%/*}\""
+
 	[ "${blobs_required}" = "n" ] && \
 		newrompath="${newrompath%.rom}_noblobs.rom"