C++17ification.

C++17ification!

- Filesystem interaction now uses std::filesystem::path.
- Usage of const char*, std::string have been changed to
  std::string_view where appropriate.
- Usage of printf-style functions changed to use fmt.

src/xenia/gpu/premake5.lua

@@ -8,6 +8,7 @@ project("xenia-gpu")
   language("C++")
   links({
     "dxbc",
+    "fmt",
     "glslang-spirv",
     "snappy",
     "spirv-tools",
@@ -32,6 +33,7 @@ project("xenia-gpu-shader-compiler")
   language("C++")
   links({
     "dxbc",
+    "fmt",
     "glslang-spirv",
     "spirv-tools",
     "xenia-base",