Add a code block for the qemu-user enabled cross build environment. When using
this environment in poudriere, CC is not set to the default of /usr/bin/cc and
a cross-compile toolchain is used. We need to hand edit this so that the run
time configuration for python matches what the FreeBSD base system provides.
PR: 208282
Submitted by: manu
Approved by: portmgr (mat)