[pypy-issue] Issue #1896: pkg-config Needed to Build pypy, no useful error given (pypy/pypy)

[Campbell Barton]

New issue 1896: pkg-config Needed to Build pypy, no useful error given
https://bitbucket.org/pypy/pypy/issue/1896/pkg-config-needed-to-build-pypy-no-useful

Campbell Barton:

Running `python2 rpython/bin/rpython --opt=jit pypy/goal/targetpypystandalone.py`

Just gives a message that `libffi.h` is missing, through investigation I found that this happens because pkg-config wasn't included on my system.

This should really give an error such as **pkg-config command not found**