rewrite lto-smoke-c to rmake

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -62,7 +62,6 @@ run-make/long-linker-command-lines-cmd-exe/Makefile
 run-make/long-linker-command-lines/Makefile
 run-make/lto-linkage-used-attr/Makefile
 run-make/lto-no-link-whole-rlib/Makefile
-run-make/lto-smoke-c/Makefile
 run-make/macos-deployment-target/Makefile
 run-make/macos-fat-archive/Makefile
 run-make/manual-link/Makefile

tests/run-make/lto-smoke-c/Makefile

@@ -1,12 +0,0 @@
-# ignore-cross-compile
-include ../tools.mk
-
-# Apparently older versions of GCC segfault if -g is passed...
-CC := $(CC:-g=)
-
-all:
-	$(RUSTC) foo.rs -C lto
-	$(CC) bar.c $(call STATICLIB,foo) \
-		$(call OUT_EXE,bar) \
-		$(EXTRACFLAGS) $(EXTRACXXFLAGS)
-	$(call RUN,bar)

tests/run-make/lto-smoke-c/rmake.rs

@@ -0,0 +1,20 @@
+// LLVM's link-time-optimization (LTO) is a useful feature added to Rust in response
+// to #10741. This test uses this feature with `-C lto` alongside a native C library,
+// and checks that compilation and execution is successful.
+// See https://github.com/rust-lang/rust/issues/10741
+
+//@ ignore-cross-compile
+// Reason: the compiled binary is executed
+
+use run_make_support::{cc, extra_c_flags, extra_cxx_flags, run, rustc, static_lib_name};
+
+fn main() {
+    rustc().input("foo.rs").arg("-Clto").run();
+    cc().input("bar.c")
+        .arg(static_lib_name("foo"))
+        .out_exe("bar")
+        .args(&extra_c_flags())
+        .args(&extra_cxx_flags())
+        .run();
+    run("bar");
+}