Make sure the Swift toolchain's C++ toolchain uses the target configuration.
Make sure the Swift toolchain's C++ toolchain uses the target configuration.

When it was incorrectly using the host configuration, the C++ feature configuration was incorrect (e.g., it claims "opt" compilation mode is enabled when it's not, since that's the *host* default).

RELNOTES: None.
PiperOrigin-RevId: 235915125

bazelbuild/rules_swift,bazelbuild/rules_swift