Swift SDKs: fix toolset.linker.path not passed to -ld-path (#7021)

This reverts commit 57d0a55 and PR
#6939.

Now that swiftlang/swift-driver#1447 and its 5.10
counterpart swiftlang/swift-driver#1454 were merged,
we can reapply the fix for Swift SDKs linker metadata not being handled.

Resolves rdar://117049947.

Author: MaxDesiatov

Sources/Build/BuildManifest/LLBuildManifestBuilder+Swift.swift

@@ -83,6 +83,8 @@ extension LLBuildManifestBuilder {
             fileSystem: self.fileSystem,
             executor: executor
         )
+        try driver.checkLDPathOption(commandLine: commandLine)
+
         let jobs = try driver.planBuild()
         try self.addSwiftDriverJobs(
             for: target,
@@ -297,6 +299,8 @@ extension LLBuildManifestBuilder {
             externalTargetModuleDetailsMap: dependencyModuleDetailsMap,
             interModuleDependencyOracle: dependencyOracle
         )
+        try driver.checkLDPathOption(commandLine: commandLine)
+
         let jobs = try driver.planBuild()
         try self.addSwiftDriverJobs(
             for: targetDescription,
@@ -583,3 +587,13 @@ extension TypedVirtualPath {
         }
     }
 }
+
+extension Driver {
+    func checkLDPathOption(commandLine: [String]) throws {
+        // `-ld-path` option is only available in recent versions of the compiler: rdar://117049947
+        if let option = commandLine.first(where: { $0.hasPrefix("-ld-path") }),
+           !self.supportedFrontendFeatures.contains("ld-path-driver-option") {
+            throw LLBuildManifestBuilder.Error.ldPathDriverOptionUnavailable(option: option)
+        }
+    }
+}

Sources/Build/BuildManifest/LLBuildManifestBuilder.swift

@@ -30,6 +30,17 @@ import func TSCBasic.topologicalSort
 
 /// High-level interface to ``LLBuildManifest`` and ``LLBuildManifestWriter``.
 public class LLBuildManifestBuilder {
+    enum Error: Swift.Error {
+        case ldPathDriverOptionUnavailable(option: String)
+
+        var description: String {
+            switch self {
+            case .ldPathDriverOptionUnavailable(let option):
+                return "Unable to pass \(option), currently used version of `swiftc` doesn't support it."
+            }
+        }
+    }
+
     public enum TargetKind {
         case main
         case test

Sources/PackageModel/UserToolchain.swift

@@ -349,7 +349,11 @@ public final class UserToolchain: Toolchain {
         swiftSDK: SwiftSDK,
         environment: EnvironmentVariables
     ) throws -> [String] {
-        let swiftCompilerFlags = swiftSDK.toolset.knownTools[.swiftCompiler]?.extraCLIOptions ?? []
+        var swiftCompilerFlags = swiftSDK.toolset.knownTools[.swiftCompiler]?.extraCLIOptions ?? []
+
+        if let linker = swiftSDK.toolset.knownTools[.linker]?.path {
+            swiftCompilerFlags += ["-ld-path=\(linker)"]
+        }
 
         guard let sdkDir = swiftSDK.pathsConfiguration.sdkRootPath else {
             if triple.isWindows() {

Tests/BuildTests/BuildPlanTests.swift

@@ -3808,7 +3808,7 @@ final class BuildPlanTests: XCTestCase {
                 .cxxCompiler: .init(extraCLIOptions: [jsonFlag(tool: .cxxCompiler)]),
                 .swiftCompiler: .init(extraCLIOptions: [jsonFlag(tool: .swiftCompiler)]),
                 .librarian: .init(path: "/fake/toolchain/usr/bin/librarian"),
-                .linker: .init(extraCLIOptions: [jsonFlag(tool: .linker)]),
+                .linker: .init(path: "/fake/toolchain/usr/bin/linker", extraCLIOptions: [jsonFlag(tool: .linker)]),
             ],
             rootPaths: try UserToolchain.default.swiftSDK.toolset.rootPaths)
         let targetTriple = try Triple("armv7em-unknown-none-macho")
@@ -3889,7 +3889,9 @@ final class BuildPlanTests: XCTestCase {
         // Compile Swift Target
         let exeCompileArguments = try result.target(for: "exe").swiftTarget().compileArguments()
         let exeCompileArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .swiftCompiler), "-g", cliFlag(tool: .swiftCompiler),
+            jsonFlag(tool: .swiftCompiler),
+            "-ld-path=/fake/toolchain/usr/bin/linker",
+            "-g", cliFlag(tool: .swiftCompiler),
             .anySequence,
             "-Xcc", jsonFlag(tool: .cCompiler), "-Xcc", "-g", "-Xcc", cliFlag(tool: .cCompiler),
             // TODO: Pass -Xcxx flags to swiftc (#6491)
@@ -3912,7 +3914,9 @@ final class BuildPlanTests: XCTestCase {
         // Link Product
         let exeLinkArguments = try result.buildProduct(for: "exe").linkArguments()
         let exeLinkArgumentsPattern: [StringPattern] = [
-            jsonFlag(tool: .swiftCompiler), "-g", cliFlag(tool: .swiftCompiler),
+            jsonFlag(tool: .swiftCompiler),
+            "-ld-path=/fake/toolchain/usr/bin/linker",
+            "-g", cliFlag(tool: .swiftCompiler),
             .anySequence,
             "-Xlinker", jsonFlag(tool: .linker), "-Xlinker", cliFlag(tool: .linker),
         ]