Rename BuildDir and NinjaBuildDir.

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

Test: Presubmits.
Merged-In: I999ca62162062f27e449f83ffb00fa580d4065b8
Change-Id: I2fcd80a9e376a6842a06aa104a9f6f5c5e16f8c7

java/java_test.go

@@ -1183,7 +1183,7 @@ func checkPatchModuleFlag(t *testing.T, ctx *android.TestContext, moduleName str
 			break
 		}
 	}
-	if expected != android.StringPathRelativeToTop(ctx.Config().BuildDir(), got) {
+	if expected != android.StringPathRelativeToTop(ctx.Config().SoongOutDir(), got) {
 		t.Errorf("Unexpected patch-module flag for module %q - expected %q, but got %q", moduleName, expected, got)
 	}
 }