insane: improve buildpath warning messages

insane: improve buildpath warning messages

Instead of reporting large chunks of the work directory and not the package
name:

"File /work/corei7-64-poky-linux/libidn2/2.2.0-r0/packages-split/libidn2-dev/usr/lib/pkgconfig/libidn2.pc in package contained reference to tmpdir"

We can clean up the paths and be more useful:

"File /usr/lib/pkgconfig/libidn2.pc in package libidn2-dev contains reference to TMPDIR"

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>