libtool: compile: unable to infer tagged configuration
Steps to reproduce
Configure and compile graphviz on macOS with the quartz plugin enabled.
libtool: compile: unable to infer tagged configuration libtool: error: specify a tag with '--tag'
The problem has been observed by two MacPorts users running OS X 10.9.5 (https://trac.macports.org/ticket/62423, https://trac.macports.org/ticket/62679) and by a MacPorts automated build machine running Mac OS X 10.5.8 (https://build.macports.org/builders/ports-10.5_ppc_legacy-builder/builds/95567).
I'm the maintainer of graphviz in MacPorts. I have not been able to reproduce the build failure on my macOS 10.13.6 machine, however I am able to confirm that
--tag=CC is missing when invoking libtool to compile GVTextLayout.m, and all libtool invocations should specify the tag.
I'm not sure because the commit message does not indicate but I think this is the issue that 79aa7d77 was trying to solve. However there were two problems: the fix was added inside a conditional so that it only takes effect on Darwin 9 (Mac OS X 10.5) when in fact the fix is needed regardless of OS version, and there was a typo in the variable name in the fix so that it does not work even on Darwin 9 (Mac OS X 10.5). I'll submit a PR to fix this shortly.
I'm aware that version 2.40.1 is old, but since the code in question has not changed in your repository, I believe the problem probably affects the current version too and that the fix is still appropriate.