[compiler-rt] [compiler-rt][test][builtins] Check linker support for --start-group (PR #205610)

[Kelvin Li via llvm-commits]

kkwli wrote:

@quic-garvgupt I am just wondering if `COMPILER_RT_BAREMETAL_BUILD` works in this case.

Anyway, your suggested change works for us on AIX.

@jdenny-ornl Could you give it a try?

https://github.com/llvm/llvm-project/pull/205610