Automatically call TestingBuildParams.RelativeToTop()

Fixes the few tests that break due to this and which cannot easily be
separated into their own changes.

Bug: 183650682
Test: m nothing
Change-Id: Ia2f31213a1f114a78e66a81d89279ecde9f4c465
diff --git a/cc/sdk_test.go b/cc/sdk_test.go
index 5a3c181..61925e3 100644
--- a/cc/sdk_test.go
+++ b/cc/sdk_test.go
@@ -66,6 +66,7 @@
 		} else {
 			toFile = m.outputFile.Path()
 		}
+		toFile = toFile.RelativeToTop()
 
 		rule := from.Description("link")
 		for _, dep := range rule.Implicits {