[wasm][build] Guard libdispatch and Threads usage with HAS_LIBDISPATCH_API

[kateinoigakukun]

This is a follow-up to 5e7281b to make it possible to turn them off when building for that platform.

[kateinoigakukun]

@swift-ci test

[MaxDesiatov]

Nice catch 👍

[kateinoigakukun]

Hmm, is this build failure tracked by somewhere?

https://ci.swift.org/job/swift-corelibs-foundation-PR-macOS/356/

/Users/ec2-user/jenkins/workspace/swift-corelibs-foundation-PR-macOS/branch-main/swift-corelibs-foundation/CoreFoundation/Locale.subproj/CFLocale.c:1277:50: error: initializer element is not a compile-time constant
    static CFStringRef const kCFLocaleCodesKey = CFSTR("__kCFLocaleCodes");
                                                 ^~~~~~~~~~~~~~~~~~~~~~~~~

[MaxDesiatov]

cc @parkera for the macOS CI failure

[kateinoigakukun]

Looks like it's broken after upgrading clang in CI. I guess the upstream CoreFoundation for Apple platforms already fixed it, so I'd like to wait to sync with the upstream instead of introducing a different fix than the upstream.

[compnerd]

Not sure if this is ideal to support, but, we can leave this be for now.