Merge pull request swiftlang#2856 from compnerd/the-path-to-enlightenment

Workspace: use `ProcessEnv.path` rather `ProcessEnv.vars["PATH"]`

Author: compnerd

Sources/Workspace/UserToolchain.swift

@@ -222,7 +222,7 @@ public final class UserToolchain: Toolchain {
 
         // Get the search paths from PATH.
         let searchPaths = getEnvSearchPaths(
-            pathString: ProcessEnv.vars["PATH"], currentWorkingDirectory: localFileSystem.currentWorkingDirectory)
+            pathString: ProcessEnv.path, currentWorkingDirectory: localFileSystem.currentWorkingDirectory)
 
         self.envSearchPaths = searchPaths