In my CMake project, I’m using the code below to detect in-source builds:

cmake_minimum_required(VERSION 3.29)
project( NoInSource )

function( NoInSourceBuilds )
  if ( ${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR} )
    execute_process(COMMAND ${CMAKE_COMMAND} -E rm CMakeCache.txt)
    message(FATAL_ERROR "In-source builds are not allowed!")
  endif()
endfunction()

NoInSourceBuilds()
message( "Won't get here")

(Base on code from: Preventing in-source builds)

Is there a way to remove the generated files prior to exiting?

The code above fails to delete the CMakeCache.txt file 🙁