Use Windows file paths for fake output paths

Author: ahoppen

Tests/SourceKitLSPTests/BackgroundIndexingTests.swift

@@ -2180,20 +2180,40 @@ final class BackgroundIndexingTests: XCTestCase {
       private let libATarget = BuildTargetIdentifier(uri: try! URI(string: "build://targetA"))
       private let libBTarget = BuildTargetIdentifier(uri: try! URI(string: "build://targetB"))
 
+      private func fakeOutputPath(for file: String, in target: String) -> String {
+        #if os(Windows)
+        return #"C:\"# + target + #"\"# + file + ".o"
+        #else
+        return "/" + target + "/" + file + ".o"
+        #endif
+      }
+
       private var sources: [SourcesItem] {
         return [
           SourcesItem(
             target: libATarget,
             sources: [
-              sourceItem(for: projectRoot.appendingPathComponent("Shared.swift"), outputPath: "/LibA/Shared.swift.o"),
-              sourceItem(for: projectRoot.appendingPathComponent("LibA.swift"), outputPath: "/LibA/LibA.swift.o"),
+              sourceItem(
+                for: projectRoot.appendingPathComponent("Shared.swift"),
+                outputPath: fakeOutputPath(for: "Shared.swift", in: "LibA")
+              ),
+              sourceItem(
+                for: projectRoot.appendingPathComponent("LibA.swift"),
+                outputPath: fakeOutputPath(for: "LibA.swift", in: "LibA")
+              ),
             ]
           ),
           SourcesItem(
             target: libBTarget,
             sources: [
-              sourceItem(for: projectRoot.appendingPathComponent("Shared.swift"), outputPath: "/LibB/Shared.swift.o"),
-              sourceItem(for: projectRoot.appendingPathComponent("LibB.swift"), outputPath: "/LibB/LibB.swift.o"),
+              sourceItem(
+                for: projectRoot.appendingPathComponent("Shared.swift"),
+                outputPath: fakeOutputPath(for: "Shared.swift", in: "LibB")
+              ),
+              sourceItem(
+                for: projectRoot.appendingPathComponent("LibB.swift"),
+                outputPath: fakeOutputPath(for: "LibB.swift", in: "LibB")
+              ),
             ]
           ),
         ]