In order to reslve a long-standing issue with inter-operation
with libSystem, we have bumped the SO name for libgcc_s.
Distributions might wish to install this new version into a
structure where exisiting code is already linked with the
compiler-local libgcc_s.1 (providing symbols exported by the
now-retired libgcc_ext.10.x shims).
The replacement libgcc_s.1 forwards the symbols from the new SO.
In order to support DYLD_LIBRARY_PATH on systems (where it works)
we forward the libSystem unwinder symbols from 10.7+ and a
compiler-local version of the libgcc unwinder on earlier.
For macOS 10.4 to 10.6 this is 'bug-compatible' with existing uses.
For 10.7+ the behaviour will now actually be correct.
This should be squashed with the initial libgcc changes for PR80556
in any backport (r12-5418-gd4943ce939d)
libgcc/ChangeLog:
* config.host (*-*-darwin*): Add logic to build a shared
unwinder library for Darwin8-10.
* config/i386/t-darwin: Build legacy libgcc_s.1.
* config/rs6000/t-darwin: Likewise.
* config/t-darwin: Reorganise the EH fragments to place
them for inclusion in a shared EH lib.
* config/t-slibgcc-darwin: Build a legacy libgcc_s.1 and
the supporting pieces (all FAT libs).
* config/t-darwin-noeh: Removed.
* config/darwin-unwind.ver: New file.
* config/rs6000/t-darwin-ehs: New file.
* config/t-darwin-ehs: New file.
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