revert r44503, (left patch file in for now), this gives an error with gcc:

extern/libmv/third_party/glog/src/utilities.cc:318: error: undefined reference to 'google::InstallFailureFunction(void (*)())'

CMakeLists.txt

@@ -1497,9 +1497,9 @@ if(MSVC10)
 endif()
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-	if(WITH_IK_ITASC)
-		message(WARNING "Using Clang as CXX compiler: disabling WITH_IK_ITASC, this feature will be missing.")
-		set(WITH_IK_ITASC OFF)
+	if(WITH_LIBMV)
+		message(WARNING "Using Clang as CXX compiler: disabling WITH_LIBMV, this feature will be missing.")
+		set(WITH_LIBMV OFF)
 	endif()
 endif()
 

extern/libmv/third_party/glog/src/logging.cc

@@ -1231,14 +1231,6 @@ void LogMessage::RecordCrashReason(
 #endif
 }
 
-#if defined(HAVE___ATTRIBUTE__)
-typedef void (*fail_func_t)() __attribute__((noreturn));
-static void logging_fail() __attribute__((noreturn));
-#else
-typedef void (*fail_func_t)();
-static void logging_fail();
-#endif
-
 static void logging_fail() {
 // #if defined(_DEBUG) && defined(_MSC_VER)
 // doesn't work for my laptop (sergey)
@@ -1251,9 +1243,14 @@ static void logging_fail() {
 #endif
 }
 
-GOOGLE_GLOG_DLL_DECL fail_func_t g_logging_fail_func = &logging_fail;
+#ifdef HAVE___ATTRIBUTE__
+GOOGLE_GLOG_DLL_DECL
+void (*g_logging_fail_func)() __attribute__((noreturn)) = &logging_fail;
+#else
+GOOGLE_GLOG_DLL_DECL void (*g_logging_fail_func)() = &logging_fail;
+#endif
 
-void InstallFailureFunction(fail_func_t fail_func) {
+void InstallFailureFunction(void (*fail_func)()) {
   g_logging_fail_func = fail_func;
 }
 

extern/libmv/third_party/glog/src/utilities.h

@@ -105,7 +105,7 @@
 # undef STACKTRACE_H
 #elif defined(HAVE_LIB_UNWIND)
 # define STACKTRACE_H "stacktrace_libunwind-inl.h"
-#elif !defined(NO_FRAME_POINTER) && !defined(__clang__)
+#elif !defined(NO_FRAME_POINTER)
 # if defined(__i386__) && __GNUC__ >= 2
 #  define STACKTRACE_H "stacktrace_x86-inl.h"
 # elif defined(__x86_64__) && __GNUC__ >= 2