Installing with portmaster and OPENMP option disabled fails as follows :
===> Installing for llvm-devel-11.0.d20200706
===> Checking if llvm-devel is already installed
===> Registering installation for llvm-devel-11.0.d20200706
pkg-static: Unable to access file /usr/ports/devel/llvm-devel/work/stage/usr/local/llvm-devel/include/ompt-multiplex.h:No such file or directory
*** Error code 74
This look quite similar to Bug 242730.
A commit references this bug:
Date: Sun Jul 12 19:21:12 UTC 2020
New revision: 542092
Fix plist without OPENMP.
Reported by: firstname.lastname@example.org
Sponsored by: DARPA
Fixed, thanks for the report!