internal/buildcfg: fix typo in DWARF 5 enabling code
Fix a typo in the code that decides which GOOS values will support use
of DWARF 5 ("darwin" was not spelled correctly).
Updates #26379.
Change-Id: I3a7906d708550fcedc3a8e89d0444bf12b9143f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/656895
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com>