CMake Build: Set /permissive- (standards conformance mode) for MSVC

To make errors appear faster when developing on Windows

MSVC 2017 and later have this flag to disallow MSVC-specific C++
language extensions. Use it to make code more correct and more portable.

Set this option with add_compile_options() in root CMakeLists.txt to
apply it to all targets.

Add one #include to unittest/gtest-clang-printing.cpp as workaround for
forward template declaration bug in MSVC http://tiny.cc/fa4tpz

Change-Id: Ie0b19701ad773c79ffd2fed24fffbb1dcb29538c
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

CMakeLists.txt

@@ -60,6 +60,11 @@ endfunction()
 set_if_target(_has_svg_target Qt5::Svg)
 option(ENABLE_SVG_SUPPORT "Enable SVG support" "${_has_svg_target}")
 
+# specify standards conformance mode to MSVC 2017 and later
+if (MSVC AND MSVC_VERSION GREATER_EQUAL 1910)
+    add_compile_options(/permissive-)
+endif()
+
 add_library(OptionalSvg INTERFACE)
 if (TARGET Qt5::Svg AND ENABLE_SVG_SUPPORT)
   target_link_libraries(OptionalSvg INTERFACE Qt5::Svg)

tests/unit/unittest/gtest-clang-printing.cpp

@@ -31,6 +31,7 @@
 
 #include <clangdocumentsuspenderresumer.h>
 #include <clangreferencescollector.h>
+#include <filepathview.h>
 #include <fulltokeninfo.h>
 #include <tokenprocessor.h>