Testsuite runs LLVM tests even if llc isn't present
configure searches for
llc but sets
llc if it isn't found. Then both
make and Hadrian simply check whether the
llc command is non-null to determine whether LLVM tests should be run. As a result, LLVM tests are always run, even if LLVM isn't available.
Originally noticed in !3767 (comment 291834).