Add VCPKG_TARGET_IS_BSD and VCPKG_HOST_IS_BSD

[cqundefine]

In most places where there's a check for either FreeBSD or OpenBSD we probably want to be checking for BSD in general and this will make adding support for systems like NetBSD or DragonFly easier.

[dg0yt]

• I'm not sure it is worth rebuilding libiconv and openssl now for all triplets and users.
  (The new variable could be adopted with regular port updates.)
• IMO this variable should be complemented by a similar platform experession (bsd). This requires changes to the tool.

[cqundefine]

I'm not sure it is worth rebuilding libiconv and openssl now for all triplets and users.

Yeah for now I reverted the changes, although I left those in the scripts that wouldn't cause any port updates.

IMO this variable should be complemented by a similar platform experession (bsd). This requires changes to the tool.

I've wanted to submit the tool PR once this one gets merged, though I've submitted one now.

[cqundefine]

I can't see how those changes could cause CI failures especially on Windows/UWP, any idea what could be causing this?

[dg0yt]

Your changes to the make scripts cause rebuilds which expose the current set of baseline regressions. The baseline regressions are from this week's image updates.

You probably shouldn't update the legacy make scripts in scripts. All improvements shall go to the vcpkg-make port.

[BillyONeal]

Close and reopen to pick up #47363

[BillyONeal]

Thanks and sorry for confusion over the baseline issues.

[cqundefine]

@BillyONeal could you take a look at this OS X failure, because I'm pretty sure it's also not related to this PR

[BillyONeal]

Closed and reopened to pick up #47326 (I'm deleting all the old macOS boxes)

[BillyONeal]

The build failure is identical to most recent full build ( https://dev.azure.com/vcpkg/public/_build/results?buildId=120541&view=results )