Revert "[msan] Check qsort input."

This change breaks LLVM bootstrap with ASan and MSan.

FAILED: lib/ToolDrivers/llvm-lib/Options.inc
OptParser.td:137:1: error: Option is equivalent to
def INPUT : Option<[], "<input>", KIND_INPUT>;
^
OptParser.td:137:1: error: Other defined here
def INPUT : Option<[], "<input>", KIND_INPUT>;

This reverts commit caa48a6b.