Merge pull request #1304 from DougGregor/add-local-plugin-path

Add default plugin path `local/lib/swift/host/plugins`

Author: DougGregor

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -253,6 +253,11 @@ extension Driver {
         .appending(components: "lib", "swift", "host", "plugins")
       commandLine.appendFlag(.pluginPath)
       commandLine.appendPath(defaultPluginPath)
+
+      let localPluginPath = try toolchain.executableDir.parentDirectory
+        .appending(components: "local", "lib", "swift", "host", "plugins")
+      commandLine.appendFlag(.pluginPath)
+      commandLine.appendPath(localPluginPath)
     }
 
     // Pass down -user-module-version if we are working with a compiler that

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -6661,6 +6661,7 @@ final class SwiftDriverTests: XCTestCase {
     let job = jobs.first!
     XCTAssertTrue(job.commandLine.contains(.flag("-plugin-path")))
     XCTAssertTrue(job.commandLine.contains(.path(.absolute(try driver.toolchain.executableDir.parentDirectory.appending(components: "lib", "swift", "host", "plugins")))))
+    XCTAssertTrue(job.commandLine.contains(.path(.absolute(try driver.toolchain.executableDir.parentDirectory.appending(components: "local", "lib", "swift", "host", "plugins")))))
   }
 
   func testClangModuleValidateOnce() throws {