Windows: Configure MinGW LTO with -fno-use-linker-plugin -fwhole-program

[akien-mga]

This was actually found by @hpvb in #102867 (comment).

Paging them to better description what this does when they have some time, as it's not super clear to me how those two options interact with -flto. But tests have shown that it solves the two linked issues.

• Works around and closes MinGW GCC LTO internal compiler error when linking: cannot read 'LTO_section_decls' #102867.
• Works around and closes VideoStreamPlayer causes game to crash upon playing video #102982.

I'll make a test build from this PR to validate this and get others to test.

[hpvb]

This should set the flags we tested. LGTM

[akien-mga]

I put the flags on the wrong branch, they apply for LLVM and not GCC :D
Will fix.

[akien-mga]

Test build from this PR: https://editor.godotengine.org/testing/4.4.rc1-test-lto-whole-program/

[BlueCube3310]

Tested on Windows 10, can confirm it fixes the issue

[akien-mga]

Tested too on Linux with Wine (both win32 and win64 builds) and the MRP from #102982 works.

Let's merge, test in 4.4.rc1 and see if there are any other downsides to these new flags.

[akien-mga]

Thanks @hpvb for looking into this!

[wildlachs]

I think this broke my build pipeline.

This is how I build my windows production build:

# Windows production build
scons platform=windows \
    target=template_release \
    arch=x86_64 \
    use_llvm=yes \
    linker=mold \
    precision=double \
    production=yes \
    scu_build=yes \
    scu_limit=1024 \
    optimize=speed

Using MinGW64 running on Fedora 41:

$ x86_64-w64-mingw32-gcc --version
x86_64-w64-mingw32-gcc (GCC) 14.2.1 20240801 (Fedora MinGW 14.2.1-3.fc41)
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Output of build process:

scons: Reading SConscript files ...
Auto-detected 12 CPU cores available for build parallelism. Using 11 cores by default. You can override it with the `-j` or `num_jobs` arguments.
SCU: Generating build files... (max includes per SCU: 1024)
Using MinGW, arch x86_64
Building for platform "windows", architecture "x86_64", target "template_release".
Using LTO: full
Checking for C header file mntent.h... (cached) no
scons: done reading SConscript files.
scons: Building targets ...
[ 75%] Compiling scene/gui/scu/scu_scene_gui.gen.cpp ...
[ 77%] Compiling scene/resources/scu/scu_scene_resources.gen.cpp ...
[ 94%] /usr/lib/gcc/x86_64-w64-mingw32/14.2.1/../../../../x86_64-w64-mingw32/bin/as: scene/gui/scu/scu_scene_gui.gen.windows.template_release.double.x86_64.o: too many sections (38865)
/tmp/ccyyzFXX.s: Assembler messages:
/tmp/ccyyzFXX.s: Fatal error: can't write 1 byte to section .text of scene/gui/scu/scu_scene_gui.gen.windows.template_release.double.x86_64.o: 'file too big'
/usr/lib/gcc/x86_64-w64-mingw32/14.2.1/../../../../x86_64-w64-mingw32/bin/as: scene/gui/scu/scu_scene_gui.gen.windows.template_release.double.x86_64.o: too many sections (38865)
/tmp/ccyyzFXX.s: Fatal error: scene/gui/scu/scu_scene_gui.gen.windows.template_release.double.x86_64.o: file too big
scons: *** [scene/gui/scu/scu_scene_gui.gen.windows.template_release.double.x86_64.o] Error 1
/usr/lib/gcc/x86_64-w64-mingw32/14.2.1/../../../../x86_64-w64-mingw32/bin/as: scene/resources/scu/scu_scene_resources.gen.windows.template_release.double.x86_64.o: too many sections (56069)
/tmp/ccwG5nE5.s: Assembler messages:
/tmp/ccwG5nE5.s: Fatal error: can't write 7 bytes to section .text of scene/resources/scu/scu_scene_resources.gen.windows.template_release.double.x86_64.o: 'file too big'
/usr/lib/gcc/x86_64-w64-mingw32/14.2.1/../../../../x86_64-w64-mingw32/bin/as: scene/resources/scu/scu_scene_resources.gen.windows.template_release.double.x86_64.o: too many sections (56069)
/tmp/ccwG5nE5.s: Fatal error: scene/resources/scu/scu_scene_resources.gen.windows.template_release.double.x86_64.o: file too big
scons: *** [scene/resources/scu/scu_scene_resources.gen.windows.template_release.double.x86_64.o] Error 1
scons: building terminated because of errors.
INFO: Time elapsed: 00:01:56.52

I am using an scu build with maximum limit because I hope the compiler is able to perform the maximal level of optimization this way. With beta4 it worked, but now it's throwing "file too big" errors.

When I build with the same settings, but without scu enabled, everything builds fine.