Regard out/soong/release-config as a source directory

Files in out/soong/release-config are generated from lunch or kati
configuration phase. They don't have rules in ninja, but always
provided as source files.

Bug: 324996303
Test: m checkbuild
Change-Id: Ibfb76a8c58a81a4d768b29d80151fa47e2ebb9c1

ui/build/test_build.go

@@ -79,6 +79,10 @@ func testForDanglingRules(ctx Context, config Config) {
 	// bpglob is built explicitly using Microfactory
 	bpglob := filepath.Join(config.SoongOutDir(), "bpglob")
 
+	// release-config files are generated from the initial lunch or Kati phase
+	// before running soong and ninja.
+	releaseConfigDir := filepath.Join(outDir, "soong", "release-config")
+
 	danglingRules := make(map[string]bool)
 
 	scanner := bufio.NewScanner(stdout)
@@ -93,7 +97,8 @@ func testForDanglingRules(ctx Context, config Config) {
 			line == variablesFilePath ||
 			line == dexpreoptConfigFilePath ||
 			line == buildDatetimeFilePath ||
-			line == bpglob {
+			line == bpglob ||
+			strings.HasPrefix(line, releaseConfigDir) {
 			// Leaf node is in one of Soong's bootstrap directories, which do not have
 			// full build rules in the primary build.ninja file.
 			continue