Remove unused extern cmake project

extern/CMakeProject-cppformat.cmake

@@ -1,34 +0,0 @@
-if(NOT IS_DIRECTORY "${SM_EXTERN_DIR}/cppformat")
-  message(
-    ERROR
-    "Submodule for cppformat missing. Run git submodule init && git submodule update first."
-    )
-  return()
-endif()
-
-list(APPEND CPPFORMAT_SRC "cppformat/fmt/format.cc")
-
-list(APPEND CPPFORMAT_HPP "cppformat/fmt/format.h")
-
-source_group("" FILES ${CPPFORMAT_SRC} ${CPPFORMAT_HPP})
-
-add_library("cppformat" ${CPPFORMAT_SRC} ${CPPFORMAT_HPP})
-
-set_property(TARGET "cppformat" PROPERTY FOLDER "External Libraries")
-
-disable_project_warnings("cppformat")
-
-target_include_directories("cppformat" PUBLIC "cppformat")
-
-if(MSVC)
-  target_compile_definitions("cppformat" PRIVATE _CRT_SECURE_NO_WARNINGS)
-elseif(APPLE)
-  set_target_properties("cppformat"
-                        PROPERTIES XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD
-                                   "${SM_CPP_STANDARD}"
-                                   XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY
-                                   "libc++")
-  target_compile_options("cppformat" PRIVATE "-std=${SM_CPP_STANDARD}" "-stdlib=libc++")
-else() # Unix
-  target_compile_options("cppformat" PRIVATE "-std=${SM_CPP_STANDARD}")
-endif()