Remove dependency on Cargo from apple-c-available-links test

Author: madsmtm

tests/run-make/apple-c-available-links/Cargo.toml

@@ -1,5 +1,6 @@
 int foo(void) {
-    // Use some API that's a lot newer than the host
+    // Use some API that's a lot newer than the deployment target.
+    // This forces Clang to insert a call to __isPlatformVersionAtLeast.
     if (__builtin_available(
         macos 1000.0,
         ios 1000.0,

tests/run-make/apple-c-available-links/build.rs

@@ -3,9 +3,15 @@
 
 //@ only-apple __builtin_available is (mostly) specific to Apple platforms.
 
-use run_make_support::{cargo, path, target};
+use run_make_support::{cc, rustc, target};
 
 fn main() {
-    let target_dir = path("target");
-    cargo().args(&["build", "--target", &target()]).env("CARGO_TARGET_DIR", &target_dir).run();
+    // Invoke the C compiler to generate an object file.
+    //
+    // (We cheat a bit here, and use the `rustc` target tuple directly as the
+    // Clang tuple, though that might not work for older Clang versions).
+    cc().arg("-target").arg(target()).arg("-c").input("foo.c").output("foo.o").run();
+
+    // Link the object file together with a Rust program.
+    rustc().target(target()).input("main.rs").link_arg("foo.o").run();
 }