Changes

[analyzer] VforkChecker: allow execve after vfork.

In the path-sensitive vfork() checker that keeps a list of operations
allowed after a successful vfork(), unforget to include execve() in the list.

Patch by Jan Včelák!

Differential Revision: https://reviews.llvm.org/D73629

[analyzer] Teach scan-build how to rebuild index.html without analyzing.

This is useful for performing custom build system integration that works by appending '--analyze --analyzer-output html' to all clang build commands.
For such users there is now still a way to have the fancy index.html file
in the output.

Differential Revision: https://reviews.llvm.org/D74467

[X86] Move avx512 code that forces zeros to the false side of vselects above a check for legal types.

This helps this transform occur earlier so we can fold the not
with setcc. If we delay it until after type legalization we might
have introduced instructions to widen the mask if the vselect was
widened. This can prevent the not from making it to the setcc.

We could of course add more DAG combines to handle that, but
moving this earlier is easier.

Revert "[analyzer] Teach scan-build how to rebuild index.html without analyzing."

This reverts commit a807a068e6ae58c6b53ad9b0b2004ea0ed0a939f.

Buildbot failures :)