rewrite target-without-atomic-cas to rmake

Author: Oneirical

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -162,9 +162,6 @@ run-make/symbol-mangling-hashed/Makefile
 run-make/symbol-visibility/Makefile
 run-make/symbols-include-type-name/Makefile
 run-make/sysroot-crates-are-unstable/Makefile
-run-make/target-cpu-native/Makefile
-run-make/target-specs/Makefile
-run-make/target-without-atomic-cas/Makefile
 run-make/test-benches/Makefile
 run-make/test-harness/Makefile
 run-make/thumb-none-cortex-m/Makefile

tests/run-make/target-without-atomic-cas/Makefile

@@ -0,0 +1,16 @@
+// ARM Cortex-M are a class of processors supported by the rust compiler. However,
+// they cannot support any atomic features, such as Arc. This test simply prints
+// the configuration details of one Cortex target, and checks that the compiler
+// does not falsely list atomic support.
+// See https://github.com/rust-lang/rust/pull/36874
+
+use run_make_support::rustc;
+
+// The target used below doesn't support atomic CAS operations. Verify that's the case
+fn main() {
+    rustc()
+        .print("cfg")
+        .target("thumbv6m-none-eabi")
+        .run()
+        .assert_stdout_not_contains(r#"target_has_atomic="ptr""#);
+}