Reapply r355803 (by mmel):

Fix LLVM libunwnwind _Unwind_Backtrace symbol version for ARM.
In original GNU libgcc, _Unwind_Backtrace is published with GCC_3.3 version
for all architectures but ARM. For ARM should be publishes with GCC_4.3.0
version. This was originally omitted in r255095, fixed in r318024 and omitted
aging in LLVM libunwind implementation in r354347.

For ARM _Unwind_Backtrace should be published as default with GCC_4.3.0
version , (because this is right original version) and again as
normal(not-default) with GCC_3.3 version (to maintain ABI compatibility
compiled/linked with wrong pre r318024 libgcc)

PR: 233664
(cherry picked from commit e8141ad1df2098dd3f6d627c49ce99307315f5fd)