Only run configure scripts for verbs that need a build

Only run configure scripts for verbs that need a build

In systemd, we want to use configure scripts to determine whether
qemu was built with support for specific devices and skip running
a test if it wasn't, or otherwise add the device to the qemu arguments.

To make this work, we need to run the configure scripts with the
default tools tree available if one is configured.

Let's change the behavior of configure scripts to only run for verbs
that need a build and run them after building the default tools tree
so that they can be run with the tools tree mounted.