port tests/ui/linkage-attr/framework to run-make

this makes it much easier to understand test failures.

before:
```
diff of stderr:

1 error: linking with `LINKER` failed: exit status: 1
2    |
-            ld: Undefined symbols:
4              _CFRunLoopGetTypeID, referenced from:
5            clang: error: linker command failed with exit code 1 (use -v to see invocation)
```

after:
```
=== HAYSTACK ===
error: linking with `cc` failed: exit status: 1
  |
  = note: use `--verbose` to show all linker arguments
  = note: Undefined symbols for architecture arm64:
            "_CFRunLoopGetTypeID", referenced from:
                main::main::hbb553f5dda62d3ea in main.main.d17f5fbe6225cf88-cgu.0.rcgu.o
          ld: symbol(s) not found for architecture arm64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

error: aborting due to 1 previous error

=== NEEDLE ===
_CFRunLoopGetTypeID\.?, referenced from:
thread 'main' panicked at /Users/jyn/git/rust-lang/rust/tests/run-make/linkage-attr-framework/rmake.rs:22:10:
needle was not found in haystack
```

this also fixes a failure related to missing whitespace; we don't actually care about whitespace in this test.

tests/run-make/linkage-attr-framework/main.rs

@@ -0,0 +1,17 @@
+#![cfg_attr(any(weak, both), feature(link_arg_attribute))]
+
+#[cfg_attr(any(link, both), link(name = "CoreFoundation", kind = "framework"))]
+#[cfg_attr(
+    any(weak, both),
+    link(name = "-weak_framework", kind = "link-arg", modifiers = "+verbatim"),
+    link(name = "CoreFoundation", kind = "link-arg", modifiers = "+verbatim")
+)]
+extern "C" {
+    fn CFRunLoopGetTypeID() -> core::ffi::c_ulong;
+}
+
+fn main() {
+    unsafe {
+        CFRunLoopGetTypeID();
+    }
+}

tests/run-make/linkage-attr-framework/rmake.rs

@@ -0,0 +1,26 @@
+//! Check that linking frameworks on Apple platforms works.
+
+//@ only-apple
+
+use run_make_support::{Rustc, run, rustc};
+
+fn compile(cfg: &str) -> Rustc {
+    let mut rustc = rustc();
+    rustc.cfg(cfg).input("main.rs");
+    rustc
+}
+
+fn main() {
+    for cfg in ["link", "weak", "both"] {
+        compile(cfg).run();
+        run("main");
+    }
+
+    let errs = compile("omit").run_fail();
+    // The linker's exact error output changes between Xcode versions, depends on
+    // linker invocation details, and the linker sometimes outputs more warnings.
+    errs.assert_stderr_contains_regex(r"error: linking with `.*` failed");
+    errs.assert_stderr_contains_regex(r"(Undefined symbols|ld: symbol[^\s]* not found)");
+    errs.assert_stderr_contains_regex(r".?_CFRunLoopGetTypeID.?, referenced from:");
+    errs.assert_stderr_contains("clang: error: linker command failed with exit code 1");
+}