CPython --with-lto: llvm-ar lookup misses absolute clang symlinks

CPython's configure (tested 3.14.0 with clang 23.1.4) looks for llvm-ar and llvm-profdata on PATH plus one extra dir: "$(dirname $(which clang))/$(dirname $(readlink clang))". It uses plain clang (not $CC) and follows only one symlink level. An ABSOLUTE symlink ~/bin/clang -> /opt/llvm/bin/clang-23 makes that a bogus path, so configure fails with 'llvm-ar is required for a --with-lto build with clang but could not be found' even though llvm-ar sits next to the real clang. A relative symlink works. Overrides: LLVM_AR=/abs/path/llvm-ar works, but a bare name like LLVM_AR=llvm-ar-23 is ignored (autoconf AC_PATH_TOOL only honours absolute presets), so Debian-style versioned names need the full path or /usr/lib/llvm-N/bin on PATH. Same rules for LLVM_PROFDATA with --enable-optimizations.