[RuntimeLibcalls] Fix stack probes for aarch64 mingw (#172973)
Before bb993a89a873ee832d063fb566c889ca3d0c2b72, the stack probes on
aarch64 windows unconditionally called "__chkstk"; after this
refactoring, it only got "__chkstk" for MSVC environments, and no stack
probe at all for other environments.
Simplify RuntimeLibcalls.td to do the same for aarch64 as for arm,
simply adding "__chkstk" for all Windows variants, and add a test to
cover this case.