Resiprocate currently requires configure and make to be invoked in the source top dir.   This patch allows building from an externals directory so that object files and other files generated by automake and autoconf do not pollute the source tree.
Example:
# git clone https://github.com/resiprocate/resiprocate
# cd resiprocate
# autoreconf -if
# cd ..
# mkdir BUILD
# cd BUILD
# ../resiprocate/configure --prefix=`pwd`/build
# make && make install