Fix CMake Warning and tweak Linux install_headers

[tytan652]

Description

Fix this warning:

CMake Warning (dev) at cmake/Modules/ObsHelpers.cmake:43 (install):
  Target obs-frontend-api has PUBLIC_HEADER files but no PUBLIC_HEADER
  DESTINATION.
Call Stack (most recent call first):
  cmake/Modules/ObsHelpers_Linux.cmake:10 (_setup_binary_target)
  UI/obs-frontend-api/CMakeLists.txt:39 (setup_binary_target)
This warning is for project developers.  Use -Wno-dev to suppress it.

And add EXCLUDE_FROM_ALL to Linux install_headers, because even without it we still need to run cmake --install . --component obs_libraries

Motivation and Context

Fix a warning, and tweak something.

How Has This Been Tested?

Try to build a -git package (with my own PKGBUILD) which use cmake --install . --component obs_libraries, header are there.

And Cmake no longer throw the warning.

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

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.

[PatTheMav]

What's the impact on Windows? Does it create stray header files in the runDir?

[RytoEX]

What's the impact on Windows? Does it create stray header files in the runDir?

We might have to run it on CI to find out, as I think the issue resolved by #6719 was CI only. Adding Seeking Testers and re-running CI.

[RytoEX]

What's the impact on Windows? Does it create stray header files in the runDir?

No stray files from CI builds, at least.

[RytoEX]

Looks good to me. @PatTheMav ?

[PatTheMav]

I haven't tested the changes locally, but looks fine to me.

[RytoEX]

Hmm. I must have missed this when previously checking:

It seems that this creates an "include" directory inside the rundir per config. While harmless, this might need a follow-up.

[PatTheMav]

Hmm. I must have missed this when previously checking:

It seems that this creates an "include" directory inside the rundir per config. While harmless, this might need a follow-up.

That's what I expected and why I asked for review on Windows.. 😂

[RytoEX]

Hmm. I must have missed this when previously checking:
It seems that this creates an "include" directory inside the rundir per config. While harmless, this might need a follow-up.

That's what I expected and why I asked for review on Windows.. 😂

I might have just skimmed straight past the top-level rundir and gone to bin since that's what we had previously checked.