Everything in this ticket indicates a problem configuring llvm-10. The llvm-10 port has no idea that grace was the port you tried to install, so this failure has nothing to do with grace.
The log says the problem configuring llvm-10 was:
:info:configure sh: /bin/ps: Operation not permitted
:info:configure sh: /bin/ps: Operation not permitted
:info:configure CMake Error at CMakeLists.txt:658 (if):
:info:configure if given arguments:
:info:configure "VERSION_LESS" "2.7"
:info:configure Unknown arguments specified
:info:configure -- Configuring incomplete, errors occurred!
If you have other logs showing a problem with grace, file a separate ticket, however the grace log you attached to the aforementioned mailing list post did not show any error; it showed successful configuration of grace, so there's no bug there, based on that log.