[Build] Convert build system to raw cmake and remove premake layer

src/xenia/gpu/null/CMakeLists.txt

@@ -0,0 +1,7 @@
+add_library(xenia-gpu-null STATIC)
+xe_platform_sources(xenia-gpu-null ${CMAKE_CURRENT_SOURCE_DIR})
+target_include_directories(xenia-gpu-null PRIVATE
+  ${PROJECT_SOURCE_DIR}/third_party/Vulkan-Headers/include
+)
+target_link_libraries(xenia-gpu-null PUBLIC xenia-base xenia-gpu xenia-ui xenia-ui-vulkan xxhash)
+xe_target_defaults(xenia-gpu-null)

src/xenia/gpu/null/premake5.lua

@@ -1,19 +0,0 @@
-project_root = "../../../.."
-include(project_root.."/tools/build")
-
-group("src")
-project("xenia-gpu-null")
-  uuid("42FCA0B3-4C20-4532-95E9-07D297013BE4")
-  kind("StaticLib")
-  language("C++")
-  links({
-    "xenia-base",
-    "xenia-gpu",
-    "xenia-ui",
-    "xenia-ui-vulkan",
-    "xxhash",
-  })
-  includedirs({
-    project_root.."/third_party/Vulkan-Headers/include",
-  })
-  local_platform_files()