install *.so in different paths for their types

Shared libraries are now installed to different directories depending on
their types.

* NDK libraries: /system/lib/ndk
* VNDK libraries: /system/lib/vndk
* VNDK-ext libraries: /system/lib/vndk-ext
* Framework-only libraries: /system/lib
* Vendor-only libraries: /vendor/lib
* Same-process HALs: /vendor/lib/sameprocess

In addition, a new module type vndk_ext_library is added. It is almost
identical to cc_shared_library but it introduces another attribute
'extends'. This is use to reference the vndk library that this vndk-ext
library is extending.

For example, in order to extend a vndk library libFoo:

cc_library {
  name: "libFoo",
  srcs: [...]
}
---------------------
vndk_ext_library {
  name: "libFoo-extended",
  srcs: [...]
  extends: "libFoo"
}

Then, libFoo will be installed as /system/lib/vndk/libFoo.so and
libFoo-extended will be installed as /system/lib/vndk-ext/libFoo.so.
Note that file name of the latter is libFoo.so, not libFoo-extended.so:
file name of an extending module is automatically set to that of the
extended module.

Bug: 33681361
Test: build & run. Libraries must be in the correct directories.
Change-Id: Ia1eb3940605d582a252c78da0f3a5b36fdab062b
diff --git a/cc/vndk_library.go b/cc/vndk_library.go
new file mode 100644
index 0000000..cca4f3f
--- /dev/null
+++ b/cc/vndk_library.go
@@ -0,0 +1,85 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// 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 (
+	"github.com/google/blueprint"
+
+	"android/soong/android"
+	"android/soong/cc/config"
+)
+
+type vndkExtLibraryProperties struct {
+	// Name of the VNDK library module that this VNDK-ext library is extending.
+	// This library will have the same file name and soname as the original VNDK
+	// library, but will be installed in /system/lib/vndk-ext rather
+	// than /system/lib/vndk.
+	Extends string
+}
+
+type vndkExtLibraryDecorator struct {
+	*libraryDecorator
+
+	properties vndkExtLibraryProperties
+}
+
+func init() {
+	android.RegisterModuleType("vndk_ext_library", vndkExtLibraryFactory)
+}
+
+func (deco *vndkExtLibraryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags {
+	extends := deco.properties.Extends
+	if extends != "" {
+		if config.IsVndkLibrary(extends) {
+			// TODO(jiyong): ensure that the module referenced by 'extends' exists. Don't know how...
+			// Adding a dependency was not successful because it leads to circular dependency
+			// in between this and the 'extends' module.
+			// Ideally, this should be something like follows:
+			// otherCtx = findModuleByName(deco.properties.Extends)
+			// if otherCtx != nil && otherCtx.isVndk() {
+			//     deco.libaryDecorator.libName = otherCtx.getBaseName()
+			// }
+			deco.libraryDecorator.libName = extends
+		} else {
+			ctx.PropertyErrorf("extends", "%s should be a VNDK or VNDK-indirect library", extends)
+		}
+	} else {
+		ctx.PropertyErrorf("extends", "missing. A VNDK-ext library must extend existing VNDK library")
+	}
+	return deco.libraryDecorator.linkerFlags(ctx, flags)
+}
+
+func (deco *vndkExtLibraryDecorator) install(ctx ModuleContext, file android.Path) {
+	deco.libraryDecorator.baseInstaller.subDir = "vndk-ext"
+	deco.libraryDecorator.baseInstaller.install(ctx, file)
+}
+
+func vndkExtLibraryFactory() (blueprint.Module, []interface{}) {
+	module, library := NewLibrary(android.DeviceSupported)
+	library.BuildOnlyShared()
+
+	_, props := module.Init()
+
+	deco := &vndkExtLibraryDecorator{
+		libraryDecorator: library,
+	}
+
+	module.installer = deco
+	module.linker = deco
+
+	props = append(props, &deco.properties)
+
+	return module, props
+}