Final changes for clang (#570)

- Allow overriding the toolchains so I can avoid changes in my working
tree
- Squash warnings that the deps use, can't just add them as PRIVATE
compile flags because it's in the headers :(
- Squash those d3d9 warnings with a suppression instead of trying to
rewrite 400 lines of code

src/spice2x/CMakeLists.txt

@@ -109,6 +109,12 @@ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     # RapidJSON does this
     add_compile_definitions(_SILENCE_CXX17_ITERATOR_BASE_CLASS_DEPRECATION_WARNING)
 
+    add_compile_options("-Wno-nontrivial-memcall") # imgui, rapidjson
+    add_compile_options("-Wno-deprecated-builtins") # robin_hood
+    add_compile_options("-Wno-deprecated-declarations") # rapidjson
+    add_compile_options("-Wno-inconsistent-missing-override") # headsocket
+    add_compile_options("-Wno-microsoft-exception-spec") # gcc/clang have different noexcept specifiers on d3d9 COM interfaces
+
     # warnings
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wunknown-warning-option")