capture-libs: Allow patterns to be read from a file

The pressure-vessel tool used in the Steam Runtime has an increasingly
long list of graphics libraries which might be better as a file
than on the command-line.

Signed-off-by: Simon McVittie <smcv@collabora.com>
4 jobs for master in 7 minutes and 41 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
manual #37772
allowed to fail manual
build:arch
passed #37771
build:bionic

00:06:54

passed #37770
build:buster

00:06:37

passed #37769
build:stretch

00:07:41