[Bug ada/79421] gnat.dg/trampoline3.adb fails on s390x

[vogt at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79421

--- Comment #2 from Dominik Vogt <vogt at linux dot vnet.ibm.com> ---
And on a target not using function descriptors otherwise,

  #define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1

affects only Ada?