Changes

[Orc] Add setters for target options and features to
JITTargetMachineBuilder.
Also remove redundant feature initialization steps from the detectHost
method.

[ExecutionEngine] Add a jitTargetAddressToFunction utility function.
jitTargetAddressToFunction takes a JITTargetAddress and returns a
pointer of the given function pointer type suitable for calling to
invoke the function at the target address.
jitTargetAddressToFunction currently behaves the same as 
jitTargetAddressToPointer, but in the near future will be updated to
perform pointer signing on architectures that require it (e.g. arm64e).
For this reason it should always be preferred when generating callable
pointers for JIT'd functions.

[ORC] Add a runAsMain utility function to ExecutionUtils.
The runAsMain function takes a pointer to a function with a standard C
main signature, int(*)(int, char*[]), and invokes it using the given
arguments and program name. The arguments are copied into writable
temporary storage as required by the C and C++ specifications, so
runAsMain safe to use when calling main functions that modify their
arguments in-place.
This patch also uses the new runAsMain function to replace hand-rolled
versions in lli, llvm-jitlink, and the SpeculativeJIT example.

[llvm-readelf/llvm-readobj] - Check the version of SHT_GNU_verneed
section entries.
It is a follow-up for D70826 and it is similar to D70810.
SHT_GNU_verneed contains the following fields:
`vn_version`: Version of structure. This value is currently set to 1,
and will be reset if the versioning implementation is incompatibly
altered.
(https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/symversion.html)
We should check it for correctness.
Differential revision: https://reviews.llvm.org/D70842