Global functions do not have function body

[zhuanhao-wu]

From https://github.com/intel/systemc-compiler/blob/main/tests/method/test_empty_sensvty4_fail.cpp
(A similar issue in https://github.com/intel/systemc-compiler/blob/main/tests/method/test_fcall_const_eval2.cpp)
/systemc-compiler/tests/method/test_generic_fcall.cpp

Note: we currently do not have support for global functions.

void glob_f() {}
bool glob_g() {return 1;}


hFunction glob_f_func_3 [
  hFunctionRetType  NONAME [
    hTypeinfo  NONAME [
      hType void NOLIST
    ]
  ]
]
hFunction glob_g_func_2 [
  hFunctionRetType  NONAME [
    hTypeinfo  NONAME [
      hType bool NOLIST
    ]
  ]
]