19.0.0-2

• MSYS2 Mingw-w64 build debut.
• Mingw-w64 build does not include swr driver due to build failure.
• Mingw-w64 binaries require a CPU capable of running SSSE3 instruction set with benefit of having slightly better performance than MSVC binaries.

Build script

• Fixed script segmentation fault for Scons build in MSYS2 Mingw-w64 due to use of undefined llvmlink variable;
• Fixed MSYS2 update script so that it does not perform the initial upgrade every time.