Relax framework linking test

This test was introduced in #118644, but was over-specified in that it assumed the path of the linker was always `cc`.

Author: madsmtm

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

@@ -1,8 +1,2 @@
-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.rs

@@ -6,7 +6,8 @@
 //@ [weak]run-pass
 //@ [both]run-pass
 
-// The linker's exact error output changes between Xcode versions.
+// The linker's exact error output changes between Xcode versions, and depends
+// on linker invocation details.
 //@ compare-output-lines-by-subset
 //@ normalize-stderr-test: "Undefined symbols for architecture .*" -> "ld: Undefined symbols:"
 //@ normalize-stderr-test: "._CFRunLoopGetTypeID.," -> "_CFRunLoopGetTypeID,"