Migrate run-make/duplicate-output-flavors to rmake.rs

Author: GuillaumeGomez

Diff for: src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -31,7 +31,6 @@ run-make/dep-info-spaces/Makefile
 run-make/dep-info/Makefile
 run-make/dump-ice-to-disk/Makefile
 run-make/dump-mono-stats/Makefile
-run-make/duplicate-output-flavors/Makefile
 run-make/dylib-chain/Makefile
 run-make/emit-path-unhashed/Makefile
 run-make/emit-shared-files/Makefile

Diff for: tests/run-make/duplicate-output-flavors/Makefile

@@ -0,0 +1,6 @@
+use run_make_support::rustc;
+
+fn main() {
+    rustc().input("foo.rs").crate_type("rlib").run();
+    rustc().input("foo.rs").crate_type("rlib,rlib").run();
+}