Merge pull request swiftlang#35777 from ahoppen/sccache-not-working

[docs] Add warning that sccache isn't caching any commands since version 0.13.4

Author: varungandhi-apple

docs/HowToGuides/GettingStarted.md

@@ -128,6 +128,8 @@ Double-check that running `pwd` prints a path ending with `swift`.
 
 ### macOS
 
+⚠️ Since version 0.2.14, `sccache` no longer caches compile commands issued by `build-script` because of [sccache PR 898](https://github.com/mozilla/sccache/pull/898), since `build-script` adds the `-arch x86_64` argument twice. The instructions below may install `sccache` 0.2.14 or newer. You may want to instead download and install an older release from their [Releases page](https://github.com/mozilla/sccache/releases) until this issue is resolved.
+
 1. Install [Xcode 12.3][Xcode] or newer:
    The required version of Xcode changes frequently and is often a beta release.
    Check this document or the host information on <https://ci.swift.org> for the