- Update premake build script for VS2017+ build support.

- Update premake (for VS2019 support).
- Update Xenia build script to detect VS2017+ version.
- Update Xenia premake scripts due to updated premake.
- Fix cc override in Xenia build script.

tools/build/scripts/force_compile_as_cc.lua

@@ -21,7 +21,11 @@ if premake.override then
   -- for msvc
   premake.override(premake.vstudio.vc2010, "additionalCompileOptions", function(base, cfg, condition)
     if cfg.abspath and table.contains(forced_cc_files, cfg.abspath) then
-      _p(3,'<CompileAs %s>CompileAsCpp</CompileAs>', condition)
+      if condition == nil or condition == '' then
+        _p(3,'<CompileAs>CompileAsCpp</CompileAs>')
+      else
+        _p(3,'<CompileAs Condition="\'$(Configuration)|$(Platform)\'==\'%s\'">CompileAsCpp</CompileAs>', condition)
+      end
     end
     return base(cfg, condition)
   end)