unable to `pip install numpy` on a specific machine
If CFLAGS, CXXFLAGS, or LDFLAGS are set, it could cause this. The problem is that those environment variables override the settings in the compile script, causing problems.
Just unset them for the invocation of the pip command and you should be all set.
It looks to me that setuptools is not working correctly, setuptools has been superceded by the python "dist" utility so you might want to install that and retry the installation.