Ensure that `-g` gets passed to `swiftc` even for opt builds that want full debug symbols (for dSYMs).
Ensure that `-g` gets passed to `swiftc` even for opt builds that want full debug symbols (for dSYMs).

RELNOTES: None.
PiperOrigin-RevId: 260926662

bazelbuild/rules_swift,bazelbuild/rules_swift