Ensure directories in the Soong output dir have appropriate permissions, so that 'm clean' works.

In particular, Bazel sometimes creates directories whose files cannot be deleted.

Test: m clean used to fail after b build //system/timezone/apex:com.android.tzdata, but now it works
Test: Added integration test which fails without this change

Change-Id: I08c8feed21c31ec187fe40be513f7eb4865c8ac3

tests/run_integration_tests.sh

@@ -6,3 +6,4 @@ TOP="$(readlink -f "$(dirname "$0")"/../../..)"
 "$TOP/build/soong/tests/bootstrap_test.sh"
 "$TOP/build/soong/tests/mixed_mode_test.sh"
 "$TOP/build/soong/tests/bp2build_bazel_test.sh"
+"$TOP/build/soong/tests/soong_test.sh"

tests/soong_test.sh

@@ -0,0 +1,22 @@
+#!/bin/bash -eu
+
+set -o pipefail
+
+# Tests of Soong functionality
+
+source "$(dirname "$0")/lib.sh"
+
+function test_m_clean_works {
+  setup
+
+  # Create a directory with files that cannot be removed
+  mkdir -p out/bad_directory_permissions
+  touch out/bad_directory_permissions/unremovable_file
+  # File permissions are fine but directory permissions are bad
+  chmod a+rwx out/bad_directory_permissions/unremovable_file
+  chmod a-rwx out/bad_directory_permissions
+
+  run_soong clean
+}
+
+test_m_clean_works

ui/build/cleanbuild.go

@@ -17,6 +17,7 @@ package build
 import (
 	"bytes"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -46,9 +47,49 @@ func removeGlobs(ctx Context, globs ...string) {
 	}
 }
 
+// Based on https://stackoverflow.com/questions/28969455/how-to-properly-instantiate-os-filemode
+// Because Go doesn't provide a nice way to set bits on a filemode
+const (
+	FILEMODE_READ         = 04
+	FILEMODE_WRITE        = 02
+	FILEMODE_EXECUTE      = 01
+	FILEMODE_USER_SHIFT   = 6
+	FILEMODE_USER_READ    = FILEMODE_READ << FILEMODE_USER_SHIFT
+	FILEMODE_USER_WRITE   = FILEMODE_WRITE << FILEMODE_USER_SHIFT
+	FILEMODE_USER_EXECUTE = FILEMODE_EXECUTE << FILEMODE_USER_SHIFT
+)
+
+// Ensures that files and directories in the out dir can be deleted.
+// For example, Bazen can generate output directories where the write bit isn't set, causing 'm' clean' to fail.
+func ensureOutDirRemovable(ctx Context, config Config) {
+	err := filepath.WalkDir(config.OutDir(), func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			info, err := d.Info()
+			if err != nil {
+				return err
+			}
+			// Equivalent to running chmod u+rwx on each directory
+			newMode := info.Mode() | FILEMODE_USER_READ | FILEMODE_USER_WRITE | FILEMODE_USER_EXECUTE
+			if err := os.Chmod(path, newMode); err != nil {
+				return err
+			}
+		}
+		// Continue walking the out dir...
+		return nil
+	})
+	if err != nil && !os.IsNotExist(err) {
+		// Display the error, but don't crash.
+		ctx.Println(err.Error())
+	}
+}
+
 // Remove everything under the out directory. Don't remove the out directory
 // itself in case it's a symlink.
 func clean(ctx Context, config Config) {
+	ensureOutDirRemovable(ctx, config)
 	removeGlobs(ctx, filepath.Join(config.OutDir(), "*"))
 	ctx.Println("Entire build directory removed.")
 }