tools/Makefile: Add ynl target

Add targets to build, clean, and install ynl headers, libynl.a, and
python tooling.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250423204647.190784-1-jdamato@fastly.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>