fix the sanitizer-dylib test on non x86_64 linux hosts

Author: Jorge Aparicio

src/test/run-make/sanitizer-dylib/Makefile

@@ -1,4 +1,4 @@
 -include ../tools.mk
 
 all:
-	$(RUSTC) -Z sanitizer=leak --crate-type dylib hello.rs 2>&1 | grep -q 'Only executables and rlibs can be compiled with `-Z sanitizer`'
+	$(RUSTC) -Z sanitizer=leak --crate-type dylib --target x86_64-unknown-linux-gnu hello.rs 2>&1 | grep -q 'Only executables and rlibs can be compiled with `-Z sanitizer`'