Make test scripts return error code

Make them executable.

Signed-off-by: Antonio Niño Díaz <antonio_nd@outlook.com>

test/asm/test.sh

@@ -1,8 +1,10 @@
 fname=$(mktemp)
+rc=0
 
 for i in *.asm; do
 	../../rgbasm $i >$fname 2>&1
 	diff -u $fname ${i%.asm}.out
+	rc=$(($? || $rc))
 done
 
-exit 0
+exit $rc