On 12.2-RELEASE (where the system compiler is clang 10.0.1), the llvm dependency should be version 10 according to the comments. Instead, it depends on the highest available version 11.

The Makefile checks ${COMPILER_VERSION} <= 11 (line 249), but with clang 10.0, ${COMPILER_VERSION} is 100, contrary to its specification ("two digits") in Uses/compiler.mk .

Fix: Another painful conditional catering to both one-digit and two-digit major versions, unless compiler.mk can be persuaded to provide the major version only (or we can assume that versions 8 and 80 are not in circulation at the same time).