Fix forwarding of -ld-path to Clang (#1447)

The Clang linker driver spells this as `--ld-path` so we can't forward the argument wholesale anymore, since as of #1441 we spell it `-ld-path` in the Swift Driver.

Author: kabiroberai

Sources/SwiftDriver/Jobs/DarwinToolchain+LinkerSupport.swift

@@ -181,7 +181,9 @@ extension DarwinToolchain {
       commandLine.appendFlag("-fuse-ld=\(arg.asSingle)")
     }
 
-    try commandLine.appendLast(.ldPath, from: &parsedOptions)
+    if let arg = parsedOptions.getLastArgument(.ldPath)?.asSingle {
+      commandLine.append(.joinedOptionAndPath("--ld-path=", try VirtualPath(path: arg)))
+    }
 
     let fSystemArgs = parsedOptions.arguments(for: .F, .Fsystem)
     for opt in fSystemArgs {

Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift

@@ -101,7 +101,9 @@ extension GenericUnixToolchain {
         }
       }
 
-      try commandLine.appendLast(.ldPath, from: &parsedOptions)
+      if let arg = parsedOptions.getLastArgument(.ldPath)?.asSingle {
+        commandLine.append(.joinedOptionAndPath("--ld-path=", try VirtualPath(path: arg)))
+      }
 
       // Configure the toolchain.
       //

Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift

@@ -43,7 +43,9 @@ extension WebAssemblyToolchain {
         commandLine.appendFlag("-fuse-ld=\(linkerArg)")
       }
 
-      try commandLine.appendLast(.ldPath, from: &parsedOptions)
+      if let arg = parsedOptions.getLastArgument(.ldPath)?.asSingle {
+        commandLine.append(.joinedOptionAndPath("--ld-path=", try VirtualPath(path: arg)))
+      }
 
       // Configure the toolchain.
       //

Sources/SwiftDriver/Jobs/WindowsToolchain+LinkerSupport.swift

@@ -105,7 +105,9 @@ extension WindowsToolchain {
       commandLine.appendFlag("-fuse-ld=lld")
     }
 
-    try commandLine.appendLast(.ldPath, from: &parsedOptions)
+    if let arg = parsedOptions.getLastArgument(.ldPath)?.asSingle {
+      commandLine.append(.joinedOptionAndPath("--ld-path=", try VirtualPath(path: arg)))
+    }
 
     switch lto {
     case .some(.llvmThin):

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -1694,7 +1694,7 @@ final class SwiftDriverTests: XCTestCase {
       let cmd = linkJob.commandLine
       XCTAssertTrue(cmd.contains(.flag("-dynamiclib")))
       XCTAssertTrue(cmd.contains(.flag("-fuse-ld=foo")))
-      XCTAssertTrue(cmd.contains(.joinedOptionAndPath("-ld-path=", try VirtualPath(path: "/bar/baz"))))
+      XCTAssertTrue(cmd.contains(.joinedOptionAndPath("--ld-path=", try VirtualPath(path: "/bar/baz"))))
       XCTAssertTrue(cmd.contains(.flag("--target=x86_64-apple-macosx10.15")))
       XCTAssertEqual(linkJob.outputs[0].file, try VirtualPath(path: "libTest.dylib"))