This reapplies 71d7fed3bc which was
reverted by 3e2bd82f02. This change
includes the fix for breaking the sanitizer bots.
As seen in https://bugs.llvm.org/show_bug.cgi?id=48880 the current
implementation for parsing grouped short options can return unclear
error messages. This change fixes the example given in the ticket in
which a flag is incorrectly given an argument. Also when parsing a
group we now keep reading past the first incorrect option and output
errors for all incorrect options in the group.
Differential Revision: https://reviews.llvm.org/D108770