Merge branch 'blender-v2.81-release'

Buildbot: Explicitly disable code signer on Linux and macOS

The script requires Python 3.7 as a very minimum, and CentOS is
only 3.6.

On macOC there was an access to a None object, due to missing
implementation of code signer on this platform.

Merge branch 'blender-v2.81-release'

Force sculpting on highest multires level

This is a workaround for T58473 to avoid likely event of ruining
sculpted data.

Differential Revision: https://developer.blender.org/D6244

Merge branch 'blender-v2.81-release'

Fix T71503: Wrap + displace + multires + Sculpt crash

The root of the issue goes to the discontinuity between the way how
mesh_calc_modifiers() and BKE_sculpt_multires_active() works.

At some point detection of original data usage by a modifier got
broken: the mesh_final based check is unreliable because deform-only
modifiers will create mesh_final for the connectivity information.

This made it so modifier stack evaluation would skip multires
evaluation, but the sculpt code will assume the multires is properly
applied.

This change makes it an explicit check about whether there are any
non-deform-only modifiers applied.

Pair programming and review together with Bastien, thanks!

Modifiers: Correct deform-only modifiers

There was a discontinuity between how deform-only modifiers are applied
for the case when result deform mesh is requested and when it is not.

Namely, the input mesh will always be guaranteed to present in the
former case, but not in the latter.

This change makes it so input mesh to deform-only modifiers is always
at consistent state.

Pair programming and review together with Bastien, thanks!

Initial implementation of code signing routines

This changes integrates code signing steps into a buildbot worker
process.

The configuration requires having a separate machine running with
a shared folder access between the signing machine and worker machine.

Actual signing is happening as a "POST-INSTALL" script run by CMake,
which allows to sign any binary which ends up in the final bundle.
Additionally, such way allows to avoid signing binaries in the build
folder (if we were signing as a built process, which iwas another
alternative).
Such complexity is needed on platforms which are using CPack to
generate final bundle: CPack runs INSTALL target into its own location,
so it is useless to run signing on a folder which is considered INSTALL
by the buildbot worker.

There is a signing script which can be used as a standalone tool,
making it possible to hook up signing for macOS's bundler.

There is a dummy Linux signer implementation, which can be activated
by returning True from mock_codesign in linux_code_signer.py.
Main purpose of this signer is to give an ability to develop the
scripts on Linux environment, without going to Windows VM.

The code is based on D6036 from Nathan Letwory.

Differential Revision: https://developer.blender.org/D6216

Cycles: Fix strict compiler warning

Pointer used for math arithmetics in assert().
CUDA device pointer is actually an integer type, not a pointer.

Codesign: Re-enable INSTALL target on Windows

Skipping INSTALL target makes it so regression tests can not be run.

Easiest and safest is to simply sign both INSTALL target and CPack.