Fix windows shared library path

Author: cachemeifyoucan

Sources/SwiftDriver/Driver/WindowsExtensions.swift

@@ -25,13 +25,12 @@ internal func executableName(_ name: String) -> String {
 
 @_spi(Testing) public func sharedLibraryName(_ name: String) -> String {
 #if canImport(Darwin)
-  let ext = ".dylib"
+  return "lib" + name + ".dylib"
 #elseif os(Windows)
-  let ext = ".dll"
+  return name + ".dll"
 #else
-  let ext = ".so"
+  return "lib" + name + ".so"
 #endif
-  return name + ext
 }
 
 // FIXME: This can be subtly wrong, we should rather

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -1188,7 +1188,7 @@ extension Driver {
 #if os(Windows)
       commandLine.appendPath(pluginPathRoot.appending(components: "bin", sharedLibraryName("SwiftInProcPluginServer")))
 #else
-      commandLine.appendPath(pluginPathRoot.appending(components: "lib", "swift", "host", sharedLibraryName("libSwiftInProcPluginServer")))
+      commandLine.appendPath(pluginPathRoot.appending(components: "lib", "swift", "host", sharedLibraryName("SwiftInProcPluginServer")))
 #endif
     }
 

Sources/SwiftDriver/Toolchains/Toolchain.swift

@@ -272,13 +272,13 @@ extension Toolchain {
        let path = try? AbsolutePath(validating: overrideString) {
       return path
     }
+    let libraryName = sharedLibraryName("_InternalSwiftScan")
 #if os(Windows)
     // no matter if we are in a build tree or an installed tree, the layout is
     // always: `bin/_InternalSwiftScan.dll`
     return try getToolPath(.swiftCompiler).parentDirectory // bin
-                                          .appending(component: "_InternalSwiftScan.dll")
+                                          .appending(component: libraryName)
 #else
-    let libraryName = sharedLibraryName("lib_InternalSwiftScan")
     let compilerPath = try getToolPath(.swiftCompiler)
     let toolchainRootPath = compilerPath.parentDirectory // bin
                                         .parentDirectory // toolchain root

Tests/SwiftDriverTests/ToolchainTests.swift

@@ -184,7 +184,7 @@ import CRT
 
     try withTemporaryDirectory { toolsDirectory in
       let customSwiftFrontend = toolsDirectory.appending(component: executableName("swift-frontend"))
-      let customSwiftScan = toolsDirectory.appending(component: sharedLibraryName("lib_InternalSwiftScan"))
+      let customSwiftScan = toolsDirectory.appending(component: sharedLibraryName("_InternalSwiftScan"))
       try localFileSystem.createSymbolicLink(customSwiftFrontend, pointingAt: defaultSwiftFrontend, relative: false)
 
       try withTemporaryDirectory { tempDirectory in