Fortran: Use -isysroot and -mmacosx-version-min= on macOS if available

Closes: #16265

Modules/CMakeFortranCompiler.cmake.in

@@ -55,6 +55,8 @@ if(CMAKE_Fortran_LIBRARY_ARCHITECTURE)
 endif()
 
 @CMAKE_Fortran_COMPILER_CUSTOM_CODE@
+@CMAKE_Fortran_SYSROOT_FLAG_CODE@
+@CMAKE_Fortran_OSX_DEPLOYMENT_TARGET_FLAG_CODE@
 
 set(CMAKE_Fortran_IMPLICIT_LINK_LIBRARIES "@CMAKE_Fortran_IMPLICIT_LINK_LIBRARIES@")
 set(CMAKE_Fortran_IMPLICIT_LINK_DIRECTORIES "@CMAKE_Fortran_IMPLICIT_LINK_DIRECTORIES@")