[many ports] Remove _find_package guards that break *_FOUND

[endrift]

Describe the pull request

Several ports add guards before calling _find_package to prevent it from being called if a package's libraries and/or includes are in cache. However, *_FOUND variables are not in the cache, and since calling find_package is generally expected to invoke the actual Find*.cmake regardless, such guards are not only unnecessary (I'm not actually sure what the point of them was in the first place), but also break CMake lists using *_FOUND if CMake is ever re-run (and MSVC loooooooooves to rerun CMake every 3 seconds).

• What does your PR fix? *_FOUND being missing if a package's libraries and/or includes are in cache

• Which triplets are supported/not supported? Have you updated the CI baseline? No changes.

• Does your PR follow the maintainer guide? Yes.

[JackBoosY]

@vicroms @ras0219 @ras0219-msft Could you please review this PR?

Thanks.

[ras0219]

LGTM -- as a bonus, would you consider adding a section to the maintainer's guide about this?

[endrift]

Wait, why? And why me? I don't see anything in there one way or the other right now. It just seemed to be a bit of a convention that broke things, but an ad hoc convention that wasn't formalized anywhere.

[cenit]

Being the author of many of them, I can just say that during the very long history of #5169 the requirement of calling find_package only if user had not already defined an include dir or library symbol become requested. That huge PR was then split into many different PRs with very long history each, so I cannot link you the exact comment about it.
If no regressions appear because of your PR, I am ok with that of course!

[endrift]

Interesting. I was wondering about the genesis of this choice. Not knowing why it was set up this way in the first place made it hard to know if it would break anything.

[endrift]

Other than me rebasing it, what's this PR waiting on?

[strega-nil]

@endrift the PR testing to run. Once it runs, I'll merge it.

[strega-nil]

Looks like this depends on yasm on osx, so we should wait for #11535 which adds yasm on osx.

[strega-nil]

/azp run

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