6 new commits pushed to

<https://github.com/RTimothyEdwards/open_pdks/tree/master|master>

by RTimothyEdwards

<https://github.com/RTimothyEdwards/open_pdks/commit/3c02c082e02ef238685001e394dca34a2d0710c0|3c02c082>

- Revised the top-level Makefile so that it does not need to declare

<https://github.com/RTimothyEdwards/open_pdks/commit/885c9719398d5727eccad6e777da780ff38ebdd8|885c9719>

- Corrected Makefile.in to build only PDKs enabled by "configure".

<https://github.com/RTimothyEdwards/open_pdks/commit/062fbb1bf3338c14420f3a9ecc0a55e19b102435|062fbb1b>

- Added generation of OPENPDKS_TOP from the configure script to

<https://github.com/RTimothyEdwards/open_pdks/commit/9a9dd2ded3865f0027e9ac4f99a3ecfdc86f63bd|9a9dd2de>

- Modified foundry_install.py so that other scripts in the common/

<https://github.com/RTimothyEdwards/open_pdks/commit/85a61ec132cd28a7a5b89b223d7ec76241a96f5d|85a61ec1>

- Corrected the comments in foundry_install.py regarding the use of

<https://github.com/RTimothyEdwards/open_pdks/commit/472ac56470453638c7f959fa010d2b3b20e88d6f|472ac564>

- Modified cdl2spi.py so that a $[model] directive on a bipolar RTimothyEdwards/open_pdks