The relevant error from the main.log might be:
CMake Error at lib/plutosdr/CMakeLists.txt:30 (target_link_libraries):
Attempt to add link library "/opt/local/lib/libgnuradio-iio.dylib" to
target "gnuradio-osmosdr" which is not built in this directory.
This is allowed only when policy CMP0079 is set to NEW.
Though I also see this which looks a little weird since the port does declare a dependency on gmp (and mpir):
-- Checking for module 'gmp'
-- Found gmp, version 6.2.1
-- Could NOT find GMP (missing: GMPXX_LIBRARY GMP_LIBRARY GMP_INCLUDE_DIR)
-- GMP not found; this is not a problem if MPIR can be found.
-- Checking for module 'mpir >= 3.0'
-- No package 'mpir' found
-- Found MPIR: /opt/local/lib/libmpirxx.dylib
-- MPIR found
-- Found MPLIB: /opt/local/lib/libmpirxx.dylib
