[Cmake][cleanup] OverloadCompilerFlags: exec_program --> execute_process.

(cherry picked from commit a1bd9774)
Signed-off-by: Steffen Müthing <muething@dune-project.org>

cmake/modules/OverloadCompilerFlags.cmake

@@ -68,7 +68,7 @@ macro(initialize_compiler_script)
     set( DEFAULT_CXX_COMPILER ${CMAKE_CXX_COMPILER} )
     set( COMPILER_SCRIPT_FILE "#!${BASH}\nexec ${CMAKE_CXX_COMPILER} \"\$@\"")
     file(WRITE ${CMAKE_BINARY_DIR}/compiler.sh "${COMPILER_SCRIPT_FILE}")
-    exec_program(${CHMOD_PROGRAM} ARGS "+x ${CMAKE_BINARY_DIR}/compiler.sh")
+    execute_process(COMMAND ${CHMOD_PROGRAM} 755 ${CMAKE_BINARY_DIR}/compiler.sh)
     set(CMAKE_CXX_COMPILER ${CMAKE_BINARY_DIR}/compiler.sh)
   endif()
 endmacro()