Closures on powerpc64-linux using static trampolines do not work when
statically linking libffi. The problem is the usage of tramp_globals.text
in libffi assumes it contains the entry point address of the first trampoline.
Powerpc's ffi_tramp_arch code returns &trampoline_code_table which for ABIs
that use function descriptors, ends up returning trampoline_code_table's
function descriptor address instead of its entry point address. Update
the code to always return the entry point address for all ABIs.
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