Handle APR / apr-util build settings properly

After being configured, APR and apr-util provide config scripts that
enumerate the libraries and compiler and linker options needed to
build code relying on APR/apr-util.  This patch causes us to more
fully include the output of these scripts in our build process.

FS-5574 --resolve
Pull out our own libuuid detection

APR is the only reason we depend on libuuid, so we'll rely on APR's
tools here.

This partially reverts commit f7fb54d0cd22c361298c772ce025a47f7937631d.