[MacPorts] #53931: clang's ld doesn't recognise "-lto_library" flag on 10.6

[MacPorts]

#53931: clang's ld doesn't recognise "-lto_library" flag on 10.6
-------------------------------------------------+-------------------------
  Reporter:  mojca                               |      Owner:  jeremyhu
      Type:  defect                              |     Status:  new
  Priority:  Normal                              |  Milestone:
 Component:  ports                               |    Version:
Resolution:                                      |   Keywords:  snowleopard
      Port:  clang-3.9 clang-4.0 llvm-3.9        |
  llvm-4.0                                       |
-------------------------------------------------+-------------------------

Comment (by kencu):

 I tried this with a fresh 10.6 VM, with basic Xcode 3.2. I did not see the
 `bits/c++config.h` issue with this clean new system, so that must be
 something specific about the older 10.6 system that I will need to clean
 up.

 First I tried changing the default ld64 to ld64-236 in the ld64 Portfile,
 but ld64-236 has a dependency on clang-3.4 to build, and clang-3.4 had a
 dependency on ld64 to build, so ld64-236 cannot be the default on 10.6.

 Leaving the default ld64 as ld64-127 on 10.6, clang-3.4 will successfully
 build, and then you can use that to build ld64-236. ld64-236 or newer is
 needed to successfully run clang-3.9 with LTO support, as above.

 So the simple step to enable 10.6 to run clang-3.9 is to first run `sudo
 port -v install ld64-236`, which will in fact build through to completion
 on an unmodified 10.6 system.

 ld64-latest has an amazing amount of build deps on 10.6, including
 llvm/clang 3.7, 3.8, AND 3.9, and I didn't start that build process
 running but I see no reason why it shouldn't complete once started.

 is it possible to set something like `ld64-236 or newer` as runtime
 dependency for clang-3.9?

--
Ticket URL: <https://trac.macports.org/ticket/53931#comment:16>
MacPorts <https://www.macports.org/>
Ports system for macOS