Remove global variables from Blueprint.

The end goal of this exercise is to remove all mutable global state so
that multiple Blueprint instances can be run in the same process.

Test: Presubmit.
Change-Id: Idb34b0920f2c7d92efb9328ce8a78b7306f89571

cmd/soong_build/main.go

@@ -158,7 +158,7 @@ func main() {
 	}
 
 	if docFile != "" {
-		if err := writeDocs(ctx, docFile); err != nil {
+		if err := writeDocs(ctx, configuration, docFile); err != nil {
 			fmt.Fprintf(os.Stderr, "%s", err)
 			os.Exit(1)
 		}