[BOLT] Fix crash while writing new profile

Summary:
New profile writer was crashing as functions were lacking a profile
flags. Fix it by requiring flags when marking function as profiled.

Generate new profile for clang. The new profile has more coverage and
results in better overall improvement from BOLT. It was generated by
merging multiple runs of:

% perf record -e cycles:u -j any,u -F32000 -- \
    ./clang bf.cpp -O2 -std=c++11 -c -o /tmp/bf.o

(cherry picked from FBD7798580)