19.0.1

• Updated Mesa3D to 19.0.1.

Build script

• Remove MSYS2 draft;
• Improve MSYS2 loader script so that it does not need a temporary shell script;
• Toolchain selection: Support release candidates and stable release of Visual Studio 2019;
• It turns out LLVM has no Meson build so remove all related code;
• LLVM/MsBuild: Compatibility with Visual Studio 2019 retaining backward compatibility with Visual Studio 2017.

Build environment updates

• scons 3.0.5a2 -> 3.0.5;
• LLVM 7.0.1 -> 8.0.0;
• Mako 1.0.7 -> 1.0.8;
• cmake 3.13.4 -> 3.14.0;
• Visual Studio 15.9.9 -> 15.9.10.

Patches and workarounds

• MSYS2: Don't patch autotools stuff.