Allow swift-corelibs-foundation to use unsafeFlags when used as a dependency

Tagged dependencies don't currently allow use of `unsafeFlags`
but we need to temporarily lift that requirement for `swift-corelibs-foundation`
that depends on C flags. In the future this would be removed
in favor of a more general mechanism for "safe" flags.

Author: xedin

Sources/Workspace/Workspace+Manifests.swift

@@ -141,9 +141,16 @@ extension Workspace {
                 let dependency = dependency.dependency
                 switch dependency.state {
                 case .sourceControlCheckout(let checkout):
-                    if checkout.isBranchOrRevisionBased {
-                        result.insert(dependency.packageRef)
+                    let packageRef = dependency.packageRef
+
+                    if checkout.isBranchOrRevisionBased
+                      // FIXME: Remove this once we have a general mechanism
+                      //        for passing "safe" flags.
+                      || packageRef.identity == .plain("swift-corelibs-foundation")
+                    {
+                      result.insert(packageRef)
                     }
+
                 case .registryDownload, .edited, .custom:
                     continue
                 case .fileSystem:

Tests/WorkspaceTests/WorkspaceTests.swift

@@ -5590,6 +5590,48 @@ final class WorkspaceTests: XCTestCase {
         }
     }
 
+    func testUnsafeFlagsInFoundation() throws {
+        let sandbox = AbsolutePath("/tmp/ws/")
+        let fs = InMemoryFileSystem()
+
+        let workspace = try MockWorkspace(
+            sandbox: sandbox,
+            fileSystem: fs,
+            roots: [
+                MockPackage(
+                    name: "Test",
+                    targets: [
+                        MockTarget(name: "Test",
+                                   dependencies: [
+                                        .product(name: "Foundation",
+                                                 package: "swift-corelibs-foundation")
+                                   ]),
+                    ],
+                    products: [],
+                    dependencies: [
+                        .sourceControl(path: "swift-corelibs-foundation", requirement: .upToNextMajor(from: "1.0.0")),
+                    ]
+                ),
+            ],
+            packages: [
+                MockPackage(
+                    name: "swift-corelibs-foundation",
+                    targets: [
+                        MockTarget(name: "Foundation", settings: [.init(tool: .swift, kind: .unsafeFlags(["-F", "/tmp"]))]),
+                    ],
+                    products: [
+                        MockProduct(name: "Foundation", targets: ["Foundation"])
+                    ],
+                    versions: ["1.0.0", nil]
+                )
+            ]
+        )
+
+        try workspace.checkPackageGraph(roots: ["Test"]) { _, diagnostics in
+            XCTAssertNoDiagnostics(diagnostics)
+        }
+    }
+
     func testEditDependencyHadOverridableConstraints() throws {
         let sandbox = AbsolutePath("/tmp/ws/")
         let fs = InMemoryFileSystem()