Implement vendor snapshot

Vendor snapshot can be captured with "m dist vendor-snapshot". With
vendor snapshot and vndk snapshot, older version of /vendor and newer
version of /system will be able to be built together by setting
BOARD_VNDK_VERSION to past vendor's version.

Only vendor modules under AOSP are to be captured. In detail, modules
under following directories are ignored:
- device/
- vendor/
- hardware/, except for interfaces/, libhardware/, libhardware_legacy/,
  and ril/

Test modules (cc_test, etc.) and sanitized modules are also ignored.

Bug: 65377115
Test: m dist vendor-snapshot
Change-Id: If7a2f6de7f36deee936930c0ccf7c47c4a0cebf6

cc/snapshot_utils.go

@@ -0,0 +1,104 @@
+// Copyright 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package cc
+
+import (
+	"strings"
+
+	"android/soong/android"
+)
+
+var (
+	headerExts = []string{".h", ".hh", ".hpp", ".hxx", ".h++", ".inl", ".inc", ".ipp", ".h.generic"}
+)
+
+type snapshotLibraryInterface interface {
+	exportedFlagsProducer
+	libraryInterface
+}
+
+var _ snapshotLibraryInterface = (*prebuiltLibraryLinker)(nil)
+var _ snapshotLibraryInterface = (*libraryDecorator)(nil)
+
+func exportedHeaders(ctx android.SingletonContext, l exportedFlagsProducer) android.Paths {
+	var ret android.Paths
+
+	// Headers in the source tree should be globbed. On the contrast, generated headers
+	// can't be globbed, and they should be manually collected.
+	// So, we first filter out intermediate directories (which contains generated headers)
+	// from exported directories, and then glob headers under remaining directories.
+	for _, path := range append(l.exportedDirs(), l.exportedSystemDirs()...) {
+		dir := path.String()
+		// Skip if dir is for generated headers
+		if strings.HasPrefix(dir, android.PathForOutput(ctx).String()) {
+			continue
+		}
+		exts := headerExts
+		// Glob all files under this special directory, because of C++ headers.
+		if strings.HasPrefix(dir, "external/libcxx/include") {
+			exts = []string{""}
+		}
+		for _, ext := range exts {
+			glob, err := ctx.GlobWithDeps(dir+"/**/*"+ext, nil)
+			if err != nil {
+				ctx.Errorf("%#v\n", err)
+				return nil
+			}
+			for _, header := range glob {
+				if strings.HasSuffix(header, "/") {
+					continue
+				}
+				ret = append(ret, android.PathForSource(ctx, header))
+			}
+		}
+	}
+
+	// Collect generated headers
+	for _, header := range append(l.exportedGeneratedHeaders(), l.exportedDeps()...) {
+		// TODO(b/148123511): remove exportedDeps after cleaning up genrule
+		if strings.HasSuffix(header.Base(), "-phony") {
+			continue
+		}
+		ret = append(ret, header)
+	}
+
+	return ret
+}
+
+func copyFile(ctx android.SingletonContext, path android.Path, out string) android.OutputPath {
+	outPath := android.PathForOutput(ctx, out)
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        android.Cp,
+		Input:       path,
+		Output:      outPath,
+		Description: "Cp " + out,
+		Args: map[string]string{
+			"cpFlags": "-f -L",
+		},
+	})
+	return outPath
+}
+
+func writeStringToFile(ctx android.SingletonContext, content, out string) android.OutputPath {
+	outPath := android.PathForOutput(ctx, out)
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        android.WriteFile,
+		Output:      outPath,
+		Description: "WriteFile " + out,
+		Args: map[string]string{
+			"content": content,
+		},
+	})
+	return outPath
+}