Add echo escape flag

Author: varkor

src/test/run-make/stdin-non-utf8/Makefile

@@ -1,5 +1,5 @@
 -include ../tools.mk
 
 all:
-	echo '\xD2' | $(RUSTC) - 2>&1 \
+	echo -e '\xD2' | $(RUSTC) - 2>&1 \
 		| $(CGREP) "error: couldn't read from stdin, as it did not contain valid UTF-8"