fix build

[alienzj]

make INCLUDE_DIRS="$PREFIX/include" LIBRARY_DIRS="$PREFIX/lib"

[alienzj]

Can we merge it?

[alienzj]

This PR is very useful for building a conda pacakage of SOAPnuke.

[youngchan919]

Thank you so much for your works. ^_^ We would also like to build the conda package. However, In the 46th line of your Makefile, the "@if test ! -d $(obj) ; " arises error in our test. Could you please fix that?

[alienzj]

I did not reproduce the problem you said.