Use proper lldb path on Windows (#890)

Author: matthewbastien

src/toolchain/toolchain.ts

@@ -345,7 +345,10 @@ export class SwiftToolchain {
      * is not in macOS toolchain path
      */
     public async getLLDB(): Promise<string> {
-        let lldbPath = path.join(this.swiftFolderPath, "lldb");
+        let lldbPath = path.join(
+            this.swiftFolderPath,
+            process.platform === "win32" ? "lldb.exe" : "lldb"
+        );
         if (!(await pathExists(lldbPath))) {
             if (process.platform !== "darwin") {
                 throw new Error("Failed to find LLDB in swift toolchain");