Make tests work again on Darwin.

aosp/1609473 broke this by making originalEnv empty unless
InitEnvironment() is called, which doesn't happen in tests.

Bug: 181835672
Test: "m nothing" on Linux and Darwin.
Change-Id: I33f9cce65a9151e620e1dddafb62d4c599ed2cac
diff --git a/android/config.go b/android/config.go
index ef5eadf..c10ad09 100644
--- a/android/config.go
+++ b/android/config.go
@@ -232,7 +232,7 @@
 
 	// Copy the real PATH value to the test environment, it's needed by
 	// NonHermeticHostSystemTool() used in x86_darwin_host.go
-	envCopy["PATH"] = originalEnv["PATH"]
+	envCopy["PATH"] = os.Getenv("PATH")
 
 	config := &config{
 		productVariables: productVariables{