Make ndk_prebuilt_* be available to any apex

The NDK prebuilts are implicitly used when building with sdk_version set.
Make the module types be available to any apex so that we don't need to
manually add apex_available property to the module definitions manually.

Bug: 150999716
Test: m

Change-Id: I0870afa4c74b4a06ab1273dff84615778561ecc9

cc/ndk_prebuilt.go

@@ -90,6 +90,11 @@ func (c *ndkPrebuiltObjectLinker) link(ctx ModuleContext, flags Flags,
 	return ndkPrebuiltModuleToPath(ctx, flags.Toolchain, objectExtension, ctx.sdkVersion())
 }
 
+func (*ndkPrebuiltObjectLinker) availableFor(what string) bool {
+	// ndk prebuilt objects are available to everywhere
+	return true
+}
+
 type ndkPrebuiltStlLinker struct {
 	*libraryDecorator
 }
@@ -103,6 +108,11 @@ func (*ndkPrebuiltStlLinker) linkerDeps(ctx DepsContext, deps Deps) Deps {
 	return deps
 }
 
+func (*ndkPrebuiltStlLinker) availableFor(what string) bool {
+	// ndk prebuilt objects are available to everywhere
+	return true
+}
+
 // ndk_prebuilt_shared_stl exports a precompiled ndk shared standard template
 // library (stl) library for linking operation. The soong's module name format
 // is ndk_<NAME>.so where the library is located under