libmodplug fails to build on macOS 10.14 Mojave

[fxcoudert]

libmodplug fails to build on macOS 10.14 Mojave (#28817) with the following error https://jenkins.brew.sh/job/Homebrew%20Mojave%20Testing/489/version=mojave_testing/testReport/junit/brew-test-bot/mojave/install_libmodplug/

libtool: link: clang++ -dynamiclib -Wl,-undefined -Wl,dynamic_lookup -o .libs/libmodplug.1.dylib  .libs/sndmix.o .libs/sndfile.o .libs/snd_fx.o .libs/snd_flt.o .libs/snd_dsp.o .libs/fastmix.o .libs/mmcmp.o .libs/load_xm.o .libs/load_wav.o .libs/load_umx.o .libs/load_ult.o .libs/load_stm.o .libs/load_s3m.o .libs/load_ptm.o .libs/load_okt.o .libs/load_mtm.o .libs/load_mod.o .libs/load_med.o .libs/load_mdl.o .libs/load_it.o .libs/load_far.o .libs/load_dsm.o .libs/load_dmf.o .libs/load_dbm.o .libs/load_ams.o .libs/load_amf.o .libs/load_669.o .libs/load_j2b.o .libs/load_mt2.o .libs/load_psm.o .libs/load_abc.o .libs/load_mid.o .libs/load_pat.o .libs/modplug.o   -lm  -g -O2 -mmacosx-version-min=10.5 -mmacosx-version-min=10.5   -install_name  /usr/local/Cellar/libmodplug/0.8.9.0/lib/libmodplug.1.dylib -compatibility_version 2 -current_version 2.0 -Wl,-single_module
ld: library not found for -lstdc++
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [libmodplug.la] Error 1
make: *** [install-recursive] Error 1

This is due to configure and configure.ac having this:

# require 10.5+ for osx/x86_64 builds
case "$host" in
        x86_64-*-darwin*)
                CXXFLAGS="$CXXFLAGS -mmacosx-version-min=10.5"
                LDFLAGS="$LDFLAGS -mmacosx-version-min=10.5" ;;
esac

[SConaway]

Other issues https://gist.github.com/c47da3fab698db366775b39d9d55249c

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[fxcoudert]

Was fixed by superenv changes.