On some systems, capnp would be installed into `lib64`, I
assume due to the use of GNUInstallDirs, however all other libs we build
in depends, go into lib/. Rather than adding lib64/ to the pkg-config
and link flags, I opted for always installing into lib/.
Co-authored-by: Ryan Ofsky <ryan@ofsky.org>
From `configure --help`:
--with-external-capnp use the system capnp binary (or the one specified
with $CAPNP) instead of compiling a new one (useful
for cross-compiling)
The non-native capnp was trying to fetch the wrong file.
Without this, "make -C depends MULTIPROCESS=1 download" is broken.
Presumably it breaks with the download target because the dependency graph is
flattened. It manages to work if native_capnp is encountered first because it
will then be found in the cache.
