[3.1.2] Build warnings in tools used when compiling using rules_swift

```bash INFO: From Compiling Swift module @@rules_swift+//tools/test_observer:test_observer: external/rules_swift+/tools/test_observer/SwiftTestingRunner.swift:83:26: warning: result of call to 'withLock' is unused 81 | switch testOrSuite { 82 | case .suite(let suiteID): 83 | discoveredSuites.withLock { $0.insert(suiteID) } | `- warning: result of call to 'withLock' is unused 84 | case .test(let test): 85 | collector.addTest(test) external/rules_swift+/tools/test_observer/SwiftTestingRunner.swift:179:34: warning: trailing closure in this context is confusable with the body of the statement; pass as a parenthesized argument to silence this warning 177 | case .string(let testID) = payload["testID"], 178 | // Ignore suites. The xUnit recorder reconstructs the hierarchy. 179 | !discoveredSuites.withLock { $0.contains(testID) }, | `- warning: trailing closure in this context is confusable with the body of the statement; pass as a parenthesized argument to silence this warning 180 | case .object(let instantJSON) = payload["instant"], 181 | case .number(let absolute) = instantJSON["absolute"] INFO: From Compiling Swift module @@rules_swift++non_module_deps+com_github_apple_swift_docc_symbolkit//:SymbolKit [for tool]: external/rules_swift++non_module_deps+com_github_apple_swift_docc_symbolkit/Sources/SymbolKit/UnifiedSymbolGraph/UnifiedSymbolGraph+Encodable.swift:44:30: warning: 'relationships' is deprecated: Use unifiedRelationships and orphanRelationships instead 42 | 43 | try container.encode(Array(symbols.values), forKey: .symbols) 44 | try container.encode(relationships, forKey: .relationships) | `- warning: 'relationships' is deprecated: Use unifiedRelationships and orphanRelationships instead 45 | } 46 | } ``` The last one appears to be out of repo, but the first two are from `//tools/test_observer`.