libarchive: pass CMAKE_INSTALL_LIBDIR

libarchive: pass CMAKE_INSTALL_LIBDIR

libarchive changed the pkgconfig install logic in 3.8.1, so that it now
installs the pkgconfig file in ${CMAKE_INSTALL_LIBDIR}/pkgconfig instead
of the previous lib/pkgconfig.

While this is a bug[1] in libarchive as this was unintended change, until
that is fixed upstream lets pass -DCMAKE_INSTALL_LIBDIR=lib to restore
previous behaviour in order for InstallDev step to install the .pc file so
other packages can find libarchive and link against it.

[1] https://github.com/libarchive/libarchive/issues/2667

Fixes: d77931df5db6 ("libarchive: bump to 3.8.1")
Signed-off-by: Robert Marko <redacted>