blender depends on nonexistent port llvm-

[ryandesign (Ryan Carsten Schmidt)]

​https://build.macports.org/builders/jobs-mirror/builds/256630/steps/mirror/logs/stdio

--->  Fetching distfiles for blender
Error: No such port: llvm-
./mpbb/mpbb: error: `mirror-distfiles' failed to run successfully

Looks like there is some situation in which the chosen compiler does not match clang-mp-([0-9]+(?:\.[0-9]+)*). For example, I found that one such situation is on Darwin 8:

$ port info --depends_lib blender os.major=8 | fold -s
Warning: All compilers are either blacklisted or unavailable; defaulting to first fallback option
depends_lib: python38, openal-soft, alembic, usd, opensubdiv, jack, libsndfile,
fftw-3, zlib, freetype, openexr, ffmpeg, opencollada, pcre, libsdl2, libpng,
openjpeg, tiff, boost, openimageio, opencolorio, openvdb, osl, embree, oidn,
tbb, potrace, libomp, gmp, glew, eigen3, lzo2, gflags, llvm-

[kencu (Ken)]

see also 61762

[ryandesign (Ryan Carsten Schmidt)]

Partial fix in [44e5416d82d0fb1564cbf93bdc46dbd30ea4c2b9/macports-ports].