With these fixes, unit tests pass with MacOS
(set DYLD_LIBRARY_PATH!)
1.) MacOS takes popen vs. pclose seriously
By using fopen we basically spoil the system and other popen
won't work.
2.) For system integrity, MacOS does not propagate DYLD_LIBRARY_PATH
to child processes such as sh. This has to be done explictly.
3.) Search the klayout binary in the right path (klayout.app/...)
4.) Reset KLAYOUT_HOME for less intervention by installed macros