The llvm.init.trampoline intrinsic is custom lowered to a call of
__trampoline_setup in the AArch64 instruction selection. As these
trampolines require an executable stack, a fatal error is reported
on Android or AArch64 Darwin platforms instead.
The function __trampoline_setup is implemented in the compiler-rt
for the AArch64 architecture.
This patch is inspired by the implementation of the same
intrinsics on the PowerPC architecture.