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

src/xenia/base/CMakeLists.txt

@@ -0,0 +1,17 @@
+add_library(xenia-base STATIC)
+xe_platform_sources(xenia-base ${CMAKE_CURRENT_SOURCE_DIR})
+# Exclude console_app_main and main_init files
+file(GLOB _base_exclude   "${CMAKE_CURRENT_SOURCE_DIR}/console_app_main_*.cc"
+  "${CMAKE_CURRENT_SOURCE_DIR}/main_init_*.cc"
+)
+get_target_property(_base_srcs xenia-base SOURCES)
+if(_base_exclude AND _base_srcs)
+  list(REMOVE_ITEM _base_srcs ${_base_exclude})
+  set_target_properties(xenia-base PROPERTIES SOURCES "${_base_srcs}")
+endif()
+target_link_libraries(xenia-base PUBLIC fmt)
+xe_target_defaults(xenia-base)
+
+if(XENIA_BUILD_TESTS)
+  add_subdirectory(testing)
+endif()