Pkg-config does not respect PKG_CONFIG_PATH
On MacOS using Mac ports I added ffmpeg6 path /opt/local/libexec/ffmpeg6/lib/pkgconfig` where pianobar and libpiano search for *.pc files and gmake cannot find those files!
Also in the variable value the defualt search paths for pkg-config should be included but on Ventura 13.6 (M2) pkg_config_path the variable was not set by default.