Nuke old SPIRV submodules from Nabla's 3rdparty and use new onces from DXC submodule

Author: AnastaZIuk

.gitmodules

@@ -1,9 +1,3 @@
-[submodule "3rdparty/SPIRV-Headers"]
-	path = 3rdparty/SPIRV-Headers
-	url = https://github.com/KhronosGroup/SPIRV-Headers.git
-[submodule "3rdparty/SPIRV-Tools"]
-	path = 3rdparty/SPIRV-Tools
-	url = https://github.com/KhronosGroup/SPIRV-Tools.git
 [submodule "3rdparty/glslang"]
 	path = 3rdparty/glslang
 	url = https://github.com/devshgraphicsprogramming/glslang.git

3rdparty/CMakeLists.txt

@@ -122,11 +122,11 @@ CACHE INTERNAL "" FORCE)
 
 set(SPIRV_HEADERS_SKIP_INSTALL ON CACHE INTERNAL "Skip SPIRV-Headers install")
 set(SPIRV_HEADERS_SKIP_EXAMPLES ON CACHE INTERNAL "Skip SPIRV-Headers examples")
-add_subdirectory(SPIRV-Headers SPIRV-Headers EXCLUDE_FROM_ALL)
+add_subdirectory(dxc/dxc/external/SPIRV-Headers dxc/external/SPIRV-Headers EXCLUDE_FROM_ALL)
 set(SKIP_SPIRV_TOOLS_INSTALL ON CACHE INTERNAL "Skip SPIRV-Tools install")
 set(SPIRV_SKIP_TESTS ON CACHE INTERNAL "Skip SPIRV-Tools tests")
 set(SPIRV_SKIP_EXECUTABLES ON CACHE INTERNAL "Skip SPIRV-Tools executable build")
-add_subdirectory(SPIRV-Tools SPIRV-Tools EXCLUDE_FROM_ALL)
+add_subdirectory(dxc/dxc/external/SPIRV-Tools dxc/external/SPIRV-Tools EXCLUDE_FROM_ALL)
 set(SKIP_GLSLANG_INSTALL ON CACHE INTERNAL "Skip glslang install")
 set(ENABLE_SPVREMAPPER OFF CACHE INTERNAL "SPVRemapper is a spirv compression experimental library")
 set(ENABLE_GLSLANG_BINARIES OFF CACHE INTERNAL "Build glslangValidator and spirv-remap?")