mageMagick's build complains
"Undefined symbols for architecture i386:
"std::__1::basic_string...".
This means most things were built with "clang++ -std=c++11 -stdlib=libc++", but the linker isn't linking to libc++ for some reason.
Two workarounds were required:
1) Using a libtool that has been built with commit c0c49f289f22ae670066657c60905986da3b555f (cherrypicking it works fine), run "libtoolize -f" to give ImageMagick a newer libtool.
2) When configuring ImageMagick, have CXXLD="clang++ -stdlib=libc++" in the environment.
Presumably #1 will be fixed by libtool-2.4.3 someday. ImageMagick's maintainer might consider using a fixed libtool sooner than that.
Dunno if #2 is a bug or not... maybe that's the way it's supposed to work.
I also had to use --disable-opencl because clparser isn't available in newer MacOSX.