Use _CFIsMainThread as a shim for pthread_main_np on Linux (#359)

Author: seabaylea

CoreFoundation/Base.subproj/CFInternal.h

@@ -787,7 +787,6 @@ CF_EXPORT void _NS_pthread_setname_np(const char *name);
 #endif
 
 #if DEPLOYMENT_TARGET_LINUX
-CF_EXPORT Boolean _CFIsMainThread(void);
 #define pthread_main_np _CFIsMainThread
 #endif
 

CoreFoundation/Base.subproj/ForSwiftFoundationOnly.h

@@ -243,6 +243,8 @@ CF_PRIVATE CF_EXPORT char *_Nullable *_Nonnull _CFEnviron(void);
 
 CF_EXPORT void CFLog1(CFLogLevel lev, CFStringRef message);
 
+CF_EXPORT Boolean _CFIsMainThread(void);
+
 _CF_EXPORT_SCOPE_END
 
 #endif /* __COREFOUNDATION_FORSWIFTFOUNDATIONONLY__ */

Foundation/NSOperation.swift

@@ -9,6 +9,12 @@
 
 #if DEPLOYMENT_ENABLE_LIBDISPATCH
 import Dispatch
+#if os(Linux)
+import CoreFoundation
+private func pthread_main_np() -> Int32 {
+    return _CFIsMainThread() ? 1 : 0
+}
+#endif
 #endif
 
 public class NSOperation : NSObject {