This patch adds 2 new machines:
and 2 new builders:
to test LLVM on Windows on Arm platform.
The machines are Microsoft Surface X Pro laptops configured for 24x7 workload.
The host build environment is bootstrapped based on LLVM 11 custom build and
uses headers and libraries from MS Visual Studio 2019. To accommodate the custom
setup we add "manual" value for "vs" parameter to ClangBuilder factory, which allows
to use manually pre-configured MSVC environment instead of initializing it during
build by running old-school vcvarsall.bat.
Finally, the bots have known failures in MCJIT unit-tests, which we are working on.
Once the failures are fixed, we'll enable unit-testsuite in both builders.