Bug: http://b/122481018
The '-keep' option of llvm-strip has changed to '-keep-section'. Update
scripts/strip.sh accordingly.
Test: Tested on various targets in AOSP and internal branch. Googlers
see http://go/clang-r349610-testing
Change-Id: Ibfc97ecdcdc305c97a4169cead1e1e3cddda9c4c