tests: support cross-compilation in run-make/rustc-macro-dep-files.

Author: eddyb

src/test/run-make/rustc-macro-dep-files/Makefile

@@ -1,6 +1,8 @@
 -include ../../run-make-fulldeps/tools.mk
 
+# FIXME(eddyb) provide `HOST_RUSTC` and `TARGET_RUSTC`
+# instead of hardcoding them everywhere they're needed.
 all:
-	$(RUSTC) foo.rs
-	$(RUSTC) bar.rs --emit dep-info
+	$(BARE_RUSTC) foo.rs --out-dir $(TMPDIR)
+	$(RUSTC) bar.rs --target $(TARGET) --emit dep-info
 	$(CGREP) -v "proc-macro source" < $(TMPDIR)/bar.d