Rename BuildDir and NinjaBuildDir.

These are just out/ and out/soong/ and the old names were quite
confusing.

Test: Presubmits.
Merged-In: I999ca62162062f27e449f83ffb00fa580d4065b8
Merged-In: I2fcd80a9e376a6842a06aa104a9f6f5c5e16f8c7
Change-Id: Ib481d2aac40df8da1b74174dc8ec576c1cb48be0
diff --git a/java/app_test.go b/java/app_test.go
index 56ad28d..07439fc 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -1737,7 +1737,7 @@
 
 			foo := result.ModuleForTests("foo", "android_common")
 
-			outSoongDir := result.Config.BuildDir()
+			outSoongDir := result.Config.SoongOutDir()
 
 			outputs := foo.AllOutputs()
 			outputMap := make(map[string]bool)