c-icap: disable Perl support

The Perl support in c-icap does not build properly, because it queries
the system-installed Perl for cflags/ldflags, which returns things
like -I/usr/local/include causing build failures since those are
invalid paths when cross-compiling.

Since there is no easy way to fix that without changing c-icap
configure.in, let's disable the Perl support for now, until someone is
interested enough to fix this up.

Fixes:

  http://autobuild.buildroot.org/results/f60/f6011ab8211589fe8e1e8932db9f8be81768d3e6/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>