Set permissions with CMake

Rather than with Unix-specific chmod command. This requires CMake `3.20`.

CMakeLists.txt

-cmake_minimum_required(VERSION 3.18)
+cmake_minimum_required(VERSION 3.20)
 project(Detection_eddies LANGUAGES Fortran)
 set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS Debug Release Profile)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")

Inst_eddies/CMakeLists.txt

@@ -15,6 +15,8 @@ target_link_libraries(inst_eddies PRIVATE Contour_531::contour_531
   Numer_Rec_95::numer_rec_95 NR_util::nr_util Jumble::jumble
   NetCDF_Fortran::netcdff)
 
-configure_file(inst_eddies.py.in inst_eddies.py @ONLY)
-execute_process(COMMAND chmod -w ${CMAKE_CURRENT_BINARY_DIR}/inst_eddies.py)
+configure_file(inst_eddies.py.in inst_eddies.py @ONLY FILE_PERMISSIONS
+  OWNER_READ OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ
+  WORLD_EXECUTE)
+
 include(Tests/CMakeLists.txt)