Adjust cmake code to support building a Windows arm64 binary on a
Windows x86/x64 host.
Add /EHsc to MSVC compiler flags for exception unwind support.
Check VCPKG_TARGET_TRIPLET in Architecture.cmake to set the appropriate
cmake variables for cross-compiling for arm64.
Add MSVC_x86_Host_Compile.cmake script, used from HostCompile.cmake, to
adjust the path of the cl.exe compiler and ENV{LIB} to build a C program
for x86 when cross-compiling, necessary for the bin2c utility.
Use wxrc from dependencies submodule when cross-compiling, because the
cross wxrc executable cannot be run on the host.
Signed-off-by: Rafael Kitover <rkitover@gmail.com>