contrib: xcb-proto is not usable

xcb-proto in contribs generates an unusable .pc file containing an unresolved reference to ${PYTHON_PREFIX}. This ultimately leads to the reverse dependency xcb package to fail to build:

checking for XCBPROTO... no
configure: error: Package requirements (xcb-proto >= 1.14) were not met:

Variable 'PYTHON_PREFIX' not defined in '/home/remi/videolan/vlc/contrib/riscv64-linux-gnu/lib/pkgconfig/xcb-proto.pc'

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables XCBPROTO_CFLAGS
and XCBPROTO_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
make: *** [../src/xcb/rules.mak:56 : .xcb] Erreur 1

xcb-proto is architecture-independent so it can easily be installed on the build system to resolve the dependency. This makes me wonder if anybody has actually tried this to use successfully from contrib?