Thread: make Thread.name return the current thread name

This makes the `name` property use the CoreFoundation SPI to query the
thread name to avoid having to have this interface be used directly in
the tests.

Author: compnerd

Foundation/Thread.swift

@@ -253,6 +253,13 @@ open class Thread : NSObject {
                 _CFThreadSetName(thread, name ?? "" )
             }
         }
+        get {
+          var buffer: [Int8] = Array<Int8>(repeating: 0, count: 128)
+          if _CFThreadGetName(&buf, Int32(buf.count)) {
+            return String(cString: buffer)
+          }
+          return nil
+        }
     }
 
 #if os(Windows)

TestFoundation/TestThread.swift

@@ -54,18 +54,7 @@ class TestThread : XCTestCase {
 
         // Compare the name set in pthreads()
         func compareThreadName(to name: String) {
-            var buf = [Int8](repeating: 0, count: 128)
-#if os(macOS) || os(iOS)
-            // Dont use _CF functions on macOS as it will break testing with Darwin's native Foundation.
-            let r = pthread_getname_np(pthread_self(), &buf, buf.count)
-#else
-            let r = _CFThreadGetName(&buf, Int32(buf.count))
-#endif
-            if r == 0 {
-                XCTAssertEqual(String(cString: buf), name)
-            } else {
-                XCTFail("Cant get thread name")
-            }
+            XCTAssertEqual(Thread.current.name, name)
         }
 
         // No name is set initially