[tools/windows.py] misplaced flag prevents gd-extensions with C files to build

[Dfred]

TL;DR

In https://github.com/godotengine/godot-cpp/blame/master/tools/windows.py#L43 -std=c++17 is set to CCFLAGS but should be set to CXXFLAGS as this prevents compilation of gd-extensions with .c files.

Background

I've been trying to use godot-sqlite's gd-extension branch with Godot4-beta3, which has godot-cpp as a submodule set to SHA 1044251.
However Godot4-beta3.exe currently fails to load the artifact built from Github actions, libgdsqlite.windows.template_debug.x86_64.dll, because of links with debug versions of VcRedist DLLs - for which I submitted issue 102.

So I've been building the sqlite gd-extension with MinGW-w64 but got trapped in DLL dependency hell. Eventually I found another pre-built toolchain / package that worked: LLVM-MinGW .

Godot-sqlite builds src/sqlite/shell.c and src/sqlite/sqlite3.c along with src/gdsqlite.cpp and src/register_types.cpp, yet that fails because scons calls:

gcc -o src\sqlite\sqlite3.o -c -std=c++17 -O2 -DDEBUG_ENABLED -DDEBUG_METHODS_ENABLED -Igodot-cpp\godot-headers -Igodot-cpp\include -Igodot-cpp\gen\include -Isrc src\sqlite\sqlite3.c
=====
error: invalid argument '-std=c++17' not allowed with 'C'

=====
scons: *** [src\sqlite\sqlite3.o] Error 1
scons: building terminated because of errors.

I tracked down the std flag to tools/windows.py and fixed the error by changing line 43 to env.Append(CXXFLAGS=["-std=c++17"]).
Then that compiled the gd-extension's dll, which loads flawlessly in Godo4-beta3 editor under Windows 10.

@Faless I hope this helps.

[Faless]

@Dfred thanks for looking into this, I've opened #908 as a fix.