pulseaudio install fails

[joerg van den hoff]

I did a (somewhat overdue, thus lengthy ...) `port upgraded outdated' yesterday and ran into some 
hickups most of which went away after forced uninstalling of affected packages and dependencies and 
reinstalling them afterwards.

however I cannot manage to get `pulseaudio' to install again (a dependency of `surf'). from the log 
file:

  2347 :info:configure checking whether C compiler accepts -std=gnu11... no
    2348 :info:configure configure: error: *** Compiler does not support -std=gnu11
    2349 :info:configure Command failed:  cd 
"/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_a 
   2349 udio_pulseaudio/pulseaudio/work/pulseaudio-14.2" && ./autogen.sh --prefix=/opt/local 
--with-mac-version-min=10.15 --with-caps --with-soxr --with-speex    2349 --disable-silent-rules 
--disable-tests --disable-gtk3 --enable-x11 --disable-oss-output --disable-alsa --disable-esound 
--disable-solaris --disable-wav   2349 eout --disable-avahi --disable-gconf --disable-gsettings 
--disable-jack --disable-asyncns --disable-tcpwrap --disable-lirc --disable-bluez5 --disable-u 
2349 dev --disable-hal-compat --disable-openssl --disable-systemd-daemon --disable-systemd-login 
--disable-systemd-journal --enable-neon-opt=no --enable-orc   2349  --enable-adrian-aec 
--with-mac-sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk
    2350 :info:configure Exit code: 1

so the `-std=gnu11' compiler flag is not recognized it seems..

this happens with 10.15.7, Xcode 12.4 and I did `xcode-select --install' when asked to do so by 
`ports' when running `port install surf'.

what am I missing? e.g., I have lost track of whether there are still issues with which 
xcode/developer tools version to use with 10.15.7 and whether I did one update too much of those or 
similar...

thanks,
joerg