Remove swiftmodule from linker filelist input

The swiftmodule isn't something the linker can operate on. It should be
passed to the clang linker, but not to the underlying linker through the
use of the linker input filelist.

This exposes itself as a linker error when trying to link with a
filelist and debug info. With debug info, the driver schedules an
`emit-module` job and an object compile job, which are both fed into the
link job.

> swiftc hello.swift -g -emit-executable -driver-filelist-threshold=0
  0: input, "hello.swift", swift
  1: emit-module, {0}, swiftmodule
  2: compile, {0}, object
  3: link, {1, 2}, image
  4: generate-dSYM, {3}, dSYM

Without generating debug info, the driver does not schedule an
emit-module job, so the swiftmodule is never generated in the first
place and not included in the filelist where it can cause trouble.

> swiftc hello.swift -emit-executable -driver-filelist-threshold=0
  0: input, "hello.swift", swift
  1: compile, {0}, object
  2: link, {1}, image

I've removed the module from the linker filelist, but kept it in the
module input list. This lines up more cleanly with the non-filelist
path, which passes the swiftmodule to the clang-linker via a direct
`-Wl,-add_ast_path`.

Fixes: rdar://125936639

Author: etcwilde

Sources/SwiftDriver/Jobs/DarwinToolchain+LinkerSupport.swift

@@ -119,7 +119,6 @@ extension DarwinToolchain {
       var inputModules = [VirtualPath]()
       for input in inputs {
         if input.type == .swiftModule && linkerOutputType != .staticLibrary {
-          inputPaths.append(input.file)
           inputModules.append(input.file)
         } else if input.type == .object {
           inputPaths.append(input.file)

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -3097,6 +3097,35 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertTrue(firstKeyOutputs.keys.contains(where: { $0 == .swiftModule }))
   }
 
+  func testLinkFilelistWithDebugInfo() throws {
+    func getFileListElements(for filelistOpt: String, job: Job) -> [VirtualPath] {
+        guard let optIdx = job.commandLine.firstIndex(of: .flag(filelistOpt)) else {
+            XCTFail("Argument '\(filelistOpt)' not in job command line")
+            return []
+        }
+        let value = job.commandLine[job.commandLine.index(after: optIdx)]
+        guard case let .path(.fileList(_, valueFileList)) = value else {
+            XCTFail("Argument wasn't a filelist")
+            return []
+        }
+        guard case let .list(inputs) = valueFileList else {
+            XCTFail("FileList wasn't a List")
+            return []
+        }
+        return inputs
+    }
+
+    var driver = try Driver(args: [
+        "swiftc", "-g", "/tmp/hello.swift", "-module-name", "Hello",
+        "-emit-library", "-driver-filelist-threshold=0"
+    ])
+
+    var jobs = try driver.planBuild()
+    XCTAssertEqual(jobs.count, 4)
+    XCTAssertEqual(getFileListElements(for: "-filelist", job: jobs[2]),
+        [.temporary(try .init(validating: "hello-1.o"))])
+  }
+
   func testDashDashPassingDownInput() throws {
     do {
       var driver = try Driver(args: ["swiftc", "-module-name=ThisModule", "-wmo", "-num-threads", "4", "-emit-module", "-o", "test.swiftmodule", "--", "main.swift", "multi-threaded.swift"])