There wasn't any good way to pass options like --host or --build
down to the pjproject configure which makes cross-compiling difficult.

* Added a new PJPROJECT_CONFIGURE_OPTS environment variable which
  can be used to pass arbitrary options to pjproject configure.
* Automatically set the pjproject configure --host and --build
  options to match those supplied for the asterisk configure.

ASTERISK-27097 #close
Reported-by: Kinsey Moore

Change-Id: I5fa776e110262851173002a26ffe1172e4c35b2e