Add option to link with libc++ on older OSX versions.

Versions of OSX lower than 10.9 link libstdc++ by default.
Also libstdc++ is linked when the osx minimum deployment target is
lower than 10.9.

The new option allows explicitly linking libc++ in the cases mentioned
above. It is not enabled by default, because most libraries and
executables on versions lower than 10.9 are compiled with libstdc++,
and mixing standard library versions can lead to crashes.

Change-Id: I7397d2bbce2cfceaeb848f25e0bbf1a24ac9bde8
Reviewed-by: Christian Tismer <tismer@stackless.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/sources/pyside2 b/sources/pyside2
-Subproject 131fdfd1a89a257094148c07c630f136752c703
+Subproject e64dda26eb2042a8c0cd7c8a33b134dcf097936