Fix missing NOTICE targets for static libs that aren't available to

platform.

The NOTICE file generation depends on the NOTICE targets for all static
library dependencies. If such a dependency didn't have
//apex_available:platform it didn't get any AndroidMk entry and hence
no NOTICE target via soong_cc_prebuilt.mk. If it was then depended upon
by a binary or library that is accessible to platform, the NOTICE
dependency failed.

Normally such a dependency is invalid, but there are corner cases where
binaries go neither into platform nor any APEX module, and they can
legitimately have such dependencies (cf. b/152241137).

With this CL requests to skip installation of such a static libraries
are ignored so that they get AndroidMk entries, which will always have
LOCAL_UNINSTALLABLE_MODULE set.

Test: "m simpleperf_ndk" with https://r.android.com/1273016, which
  removes //apex_available:platform from libs that simpleperf_ndk
  depends on statically.
Bug: 152241137
Bug: 149217815
Change-Id: If36e85dd16ade56d4ec1d6744811df5a15b6242c

cc/androidmk.go

@@ -248,6 +248,10 @@ func (library *libraryDecorator) AndroidMkEntries(ctx AndroidMkContext, entries
 			entries.SubName = "." + library.stubsVersion()
 		}
 		entries.ExtraEntries = append(entries.ExtraEntries, func(entries *android.AndroidMkEntries) {
+			// Note library.skipInstall() has a special case to get here for static
+			// libraries that otherwise would have skipped installation and hence not
+			// have executed AndroidMkEntries at all. The reason is to ensure they get
+			// a NOTICE file make target which other libraries might depend on.
 			entries.SetBool("LOCAL_UNINSTALLABLE_MODULE", true)
 			if library.buildStubs() {
 				entries.SetBool("LOCAL_NO_NOTICE_FILE", true)