Add test for Apple's -weak_framework linker argument

Author: madsmtm

tests/run-pass-valgrind/osx-frameworks.rs

@@ -0,0 +1,8 @@
+error: linking with `cc` failed: exit status: 1
+   |
+           ld: Undefined symbols:
+             _CFRunLoopGetTypeID, referenced from:
+           clang: error: linker command failed with exit code 1 (use -v to see invocation)
+
+
+error: aborting due to 1 previous error

tests/ui/linkage-attr/framework.omit.stderr

@@ -0,0 +1,30 @@
+// Check that linking frameworks on Apple platforms works.
+//@ only-macos
+//@ revisions: omit link weak both
+//@ [omit]build-fail
+//@ [link]run-pass
+//@ [weak]run-pass
+//@ [both]run-pass
+
+// The linker's exact error output changes between Xcode versions.
+//@ compare-output-lines-by-subset
+//@ normalize-stderr-test: "Undefined symbols for architecture .*" -> "ld: Undefined symbols:"
+//@ normalize-stderr-test: "._CFRunLoopGetTypeID.," -> "_CFRunLoopGetTypeID,"
+
+#![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;
+}
+
+pub fn main() {
+    unsafe {
+        CFRunLoopGetTypeID();
+    }
+}