Update appveyor file and turn off /WX for clang-msvc

win32-clang-msvc has an error when compiling with /WX. The moc_predefs.h
file is not being built correctly, while without /WX it works. The
change should be reverted to enabling /WX for all msvc compilers when
the clang-msvc issue is fixed.

Update path to clang-format in appveyor file

Retry CI on Python script

Python script failed on CI due to run-clang-format.py: error: [Error 5]
Access is denied. Research says attempting again might solve the
problem.

advancedSettings.pro

@@ -22,8 +22,13 @@ TEMPLATE = app
     QMAKE_CXXFLAGS_WARN_ON -= -W3
     #C4127 was in a third party file with no way to turn off.
     QMAKE_CXXFLAGS += /W4 /wd4127
-    QMAKE_CXXFLAGS += /WX
-
+    !*clang-msvc {
+        #win32-clang-msvc is unable to correctly build the first time
+        #with warnings as errors on. There seems to be an issue with the moc_predefs.h
+        #file not being built correctly when /WX is on. Until the issue is fixed, 
+        #win32-clang-msvc is built without /WX.
+        QMAKE_CXXFLAGS += /WX
+    }
 }
 
 *g++* {