cc: export Stripper struct

The cc stripping logic can be reused for Rust. Export the Stripper
structure for that purpose. Extract the strip-related flags from
builderFlags into StripFlags. Add the method flagsToStripFlags
(similarly to flagsToBuilderFlags).

Add the helper method disableStripping on libraryDecorator.

Test: m
Bug: 153430439
Change-Id: I11aef1abb8d498a4c1672500a7398279edf7f548
diff --git a/cc/ndk_library.go b/cc/ndk_library.go
index 58e742e..fe3efc0 100644
--- a/cc/ndk_library.go
+++ b/cc/ndk_library.go
@@ -405,7 +405,7 @@
 	library.BuildOnlyShared()
 	module.stl = nil
 	module.sanitize = nil
-	library.StripProperties.Strip.None = BoolPtr(true)
+	library.disableStripping()
 
 	stub := &stubDecorator{
 		libraryDecorator: library,