Suppress warnings for remote Clang targets

[xedin]

This mirrors behavior of remote swift targets which suppress warnings as well.

[xedin]

@MaxDesiatov what would be the best way to test this? I couldn't find any tests with -suppress-warnings flag in the suite :/

[xedin]

This is actually a draft, "package" doesn't exist for clang targets yet, I'm about open a PR to introduce that.

[xedin]

I think I figured it out - I can extend ClangTargetBuildDescriptionTests to check that by forming a remote package dependency.

[MaxDesiatov]

@MaxDesiatov what would be the best way to test this? I couldn't find any tests with -suppress-warnings flag in the suite :/

This looks like something that belongs to BuildPlanTests or maybe worth creating a new ClangTargetBuildPlanTests as the existing BuildPlanTests is too big.

[MaxDesiatov]

maybe worth creating a new ClangTargetBuildPlanTests as the existing BuildPlanTests is too big.

Turns out we already have ClangTargetBuildDescriptionTests.swift.

[xedin]

@swift-ci please test

[xedin]

@swift-ci please test Windows platform

[MaxDesiatov]

@swift-ci test windows