CMake: pro2cmake.py: Ignore 3rdparty code that gets included

Ignore include files that go into 3rdparty code. Qt 6 should work
with external libraries, so there is no need to drag in 3rdparty
include directories, etc.

Change-Id: I990f3a8a4983e1458843b4122420b9daec763ccb
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

util/cmake/pro2cmake.py

@@ -889,6 +889,9 @@ def do_include(scope: Scope, *, debug: bool = False) -> None:
         include_file = i
         if not include_file:
             continue
+        if '/3rdparty/' in include_file:
+            print('    ****: Ignoring include file in 3rdparty: {}.'.format(include_file))
+            continue
         if not os.path.isfile(include_file):
             print('    XXXX: Failed to include {}.'.format(include_file))
             continue