Subject: Support MACOSX_DEPLOYMENT_TARGET=11.0

From: Isuru Fernando <[email-masked]>
Date: Thu, 12 Nov 2020 13:39:14 -0600

Hello maintainers,

I noticed that when MACOSX_DEPLOYMENT_TARGET=11.0 is set "-Wl,-undefined"
flag is not set
because of a check in m4/libtool/m4 at
http://git.savannah.gnu.org/cgit/libtool.git/tree/m4/libtool.m4?id=b9b44533fbf7c7752ffd255c3d09cc360e24183b#n1074
that only checks for 10.*. A fix would be to check for both 10.* and 11.*

I can send a patch if you prefer.

Isuru