RUN THESE COMMANDS IN MSYS2 SHELL

1. cd /
2. pacman --noconfirm -S base-devel git
3. rm -rf MINGW-packages
4. git clone https://github.com/msys2/MINGW-packages.git
5. cd /MINGW-packages/mingw-w64-gcc
   a. Look in file PKGBUILD file for options passed to configure.
      i. In the 10.3.0 file, I changed _enable_jit=yes to _enable_jit=no (line 10)
      ii. Remove patch files with jit in the name (10.3.0) (look for apply_patch_with_msg)
           a. 0022-jit-port-libgccjit-to-Windows.patch
           b. 0023-gcc-jit-Rename-libgccjit.dll-to-libgccjit-0.dll.patch
      iii. e.g. --enable-sjlj-exceptions or --disable-sjlj-exceptions (<-preferred)
      iv. make sure options line does not have 'debug' enabled:
          options=('staticlibs' '!emptydirs') # '!strip' 'debug')]
6. pacman --noconfirm -S mingw-w64-x86_64-toolchain
7. pacman --noconfirm -S mingw-w64-i686-toolchain
8. makepkg-mingw [--skippgpcheck]  (This takes about 3.6 hours on a core i9-9900 with SSD)
   a. May need to use --skippgpcheck as option. I had to use this on 10.3.0.
   b. This may result in "unmet dependencies".
      To resolve those, just use pacman -S to install them.
9. If the package fails to make the second time, remove the pkg and src dirs
   and re-run makepkg-mingw entering this before:
   a. export MINGW_ARCH=MINGW32 (to make i686 pkg only)
10. Uncompress the .zstd packages:  zst -d *.zst

Without comments
----------------
cd /
pacman --noconfirm -S base-devel git
rm -rf MINGW-packages
git clone https://github.com/msys2/MINGW-packages.git
cd /MINGW-packages/mingw-w64-gcc
[fix PKGBUILD if necessary]
pacman --noconfirm -S mingw-w64-x86_64-toolchain
pacman --noconfirm -S mingw-w64-i686-toolchain
makepkg-mingw --skippgpcheck
zstd -d *.zst