Upgrade to MacOS 10.15.6 Catalina, More Bookkeeping Notes

./configure --prefix=/opt/sac

On MacOS Catalina 10.15.6, with Xcode Version 11.6  I also needed to update the library path in my .zshrc (the MacOSX.sdk paths are new):

export CPATH='/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include:/opt/local/include'

export LIBRARY_PATH='/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib:/opt/local/lib'

in the  .cshrc file, I added 

setenv CPATH /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include:/opt/local/include

setenv LIBRARY_PATH /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib:/opt/local/lib

but there are more things to change, before sac will compile and run ., . ..