pcr: aflplusplus: Add llvm to makedepends for llvm-config
Without that fix, with libremakepkg, we have:
| [+] llvm_mode detected llvm < 11, afl-lto LTO will not be build.
| GNUmakefile.llvm:120: we have trouble finding clang - llvm-config is not helping us
| GNUmakefile.llvm:135: we have trouble finding clang++ - llvm-config is not helping us
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>