fix: enable building without threads (#964)

CMakeLists.txt

@@ -468,6 +468,7 @@ set (GLOG_SRCS
   src/demangle.h
   src/logging.cc
   src/raw_logging.cc
+  src/signalhandler.cc
   src/symbolize.cc
   src/symbolize.h
   src/utilities.cc
@@ -475,10 +476,6 @@ set (GLOG_SRCS
   src/vlog_is_on.cc
 )
 
-if (HAVE_PTHREAD OR WIN32 OR CYGWIN)
-  list (APPEND GLOG_SRCS src/signalhandler.cc)
-endif (HAVE_PTHREAD OR WIN32 OR CYGWIN)
-
 if (CYGWIN OR WIN32)
   list (APPEND GLOG_SRCS
     src/windows/port.cc

src/googletest.h

@@ -595,7 +595,8 @@ class Thread {
   void Start() { pthread_create(&th_, nullptr, &Thread::InvokeThread, this); }
   void Join() { pthread_join(th_, nullptr); }
 #else
-# error No thread implementation.
+  void Start() {}
+  void Join() {}
 #endif
 
  protected:
@@ -614,7 +615,7 @@ class Thread {
   }
   HANDLE handle_;
   DWORD th_;
-#else
+#elif defined(HAVE_PTHREAD)
   pthread_t th_;
 #endif
 };