PROJECT(hello Fortran)
CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
FILE(WRITE s1.f "      PROGRAM Hello\n      print *,'Hello World'\n      END PROGRAM")

ADD_CUSTOM_COMMAND(
   OUTPUT s1.copy.f
   DEPENDS s1.f
   COMMAND ${CMAKE_COMMAND} -E copy s1.f s1.copy.f
   )
ADD_CUSTOM_TARGET(
   copy
   DEPENDS s1.copy.f
   SOURCES s1.f
   )

ADD_EXECUTABLE(hello s1.f)
ADD_DEPENDENCIES(hello copy)