Search for files named Blueprints only under build/blueprint

to enable other subprojects to use their own instance of
Blueprint in other directories.

Files named Android.bp are still autodetected throughout the
tree like previously.

Bug: 64363847
Test: mkdir -p subdir \
      && echo "syntax error" > Blueprints \
      && m -j nothing

Test: build/soong/scripts/diff_build_graphs.sh \
      --products=aosp_arm \
      'build/soong:work^' 'build/soong:work'

Change-Id: I8199f12b68dc1699bf44682b86169def37b53a5e

ui/build/finder.go

@@ -80,17 +80,8 @@ func FindSources(ctx Context, config Config, f *finder.Finder) {
 		ctx.Fatalf("Could not find modules: %v", err)
 	}
 
-	isBlueprintFile := func(dir finder.DirEntries) (dirs []string, files []string) {
-		files = []string{}
-		for _, file := range dir.FileNames {
-			if file == "Android.bp" || file == "Blueprints" {
-				files = append(files, file)
-			}
-		}
-
-		return dir.DirNames, files
-	}
-	androidBps := f.FindMatching(".", isBlueprintFile)
+	androidBps := f.FindNamedAt(".", "Android.bp")
+	androidBps = append(androidBps, f.FindNamedAt("build/blueprint", "Blueprints")...)
 	err = dumpListToFile(androidBps, filepath.Join(dumpDir, "Android.bp.list"))
 	if err != nil {
 		ctx.Fatalf("Could not find modules: %v", err)