Update of E2k support

[makise-homura]

Description

As of support for Elbrus has been introduced in PR #3288, this pull request improves support for building obs-studio on Elbrus hardware platform (which is based on Russian Elbrus CPU family) with its native lcc (eLbrus Compiler Collection) compiler.

Motivation and Context

It allows current master of OBS be built on Elbrus out-of-the-box (and use SIMD functionality with altered version of SIMDE as of this PR).

How Has This Been Tested?

Build and testing plan:

• Build on Elbrus workstation (e2k-linux-gnu) and run there.
• Build on x86_64 workstation (x86_64-linux-gnu) and run there (to be sure that nothing is broken on x86_64).

Details of Elbrus workstation:

• CPU: Elbrus-8C (formerly Elbrus-8S) running on 1300 MHz
• Motherboard: E8C-EATX
• OS: OS Elbrus 6.0.0
• GPU: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere Radeon RX 580 (rev e7)
• Kernel: 5.4.0-2.3-e8c
• Compiler: lcc:1.25.09:Oct--1-2020:e2k-v4-linux gcc (GCC) 7.3.0 compatible

Details of x86_64 workstation:

• CPU: AMD Ryzen Threadripper 2990WX 32-Core Processor running at 3.0 GHz
• Motherboard: MSI X399 SLI PLUS (MS-7B09)
• GPU: Advanced Micro Devices, Inc. [AMD/ATI] Caicos [Radeon HD 6450/7450/8450 / R5 230 OEM]
• OS: Ubuntu 20.04.1 LTS
• Kernel: 5.4.0-54-generic Steps to actually compile on Linux? #60-Ubuntu
• Compiler: gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0

Results:

• Successfully performed mkdir build; cd build; cmake -DCMAKE_BUILD_TYPE=Release .. && make -j16 && sudo make install, and ran obs on both workstations; no suspicious behavior found.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[kkartaltepe]

simde changes to support elbrus should be submitted upstream to the simde project (https://github.com/simd-everywhere/simde) , then we can update our simde version once those changes have been submitted. Feel free to submit a PR just for fixing the libcaption warnings.

[makise-homura]

Ok. So should I rewind this branch to ff523ab , and then force-push this branch with the only one that commit?

[kkartaltepe]

If you want to do that and rewrite the PR description thats fine too.

[makise-homura]

Okay @kkartaltepe , I filed a PR for SIMDE, and force-pushed this branch to leave only SIMDE-unrelated commit.

[jp9000]

Those libcaption warnings are already fixed on master, so this PR basically does nothing now. When your E2k changes go through and are ready, then you should make a new PR (can probably copy this PR mostly word for word when that happens). If that's okay at least.

[makise-homura]

Uh, right, I haven't checked master recently to see this commit is already there. Thanks.
I guess it's ok here then.
By the way, will there be need in a specific PR for updating SIMDE in obs-studio once my changes land into its upstream?

[jp9000]

I believe so yes. Whenever they update it, then would it be okay if you could recreate this PR with those changes? Sorry for the trouble

[makise-homura]

Yes, looks ok for me. So I'll wait till they accept my changes and then create a PR for obs-studio to pull files from updated vesrsion of SIMDE.