util: add pkg-config to ubuntu all-dependencies Dockerfiles

util: add pkg-config to ubuntu all-dependencies Dockerfiles

Without this, HDF5 is not built, e.g. a run such as
http://jenkins.gem5.org/job/Nightly/68/console contains:

Checking for hdf5-serial using pkg-config... pkg-config not found
Checking for hdf5 using pkg-config... pkg-config not found
Checking for H5Fcreate("", 0, 0, 0) in C library hdf5... (cached) no
Warning: Couldn't find any HDF5 C++ libraries. Disabling
         HDF5 support.

This is done to increase coverage a bit, and serve as dependency
documentation to users.

Change-Id: Ibf820a3aa76c29eeee1201646924ee181615a162
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34777
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>