libarchive: use -isystem for /usr/include

	. 'fixes' warnings that are in these headers, but normally aren't
	   emited as they're system headers

Change-Id: Ibd20343eae51770cef71116bbda0d9141441ec54
enable fatal warnings

	. kernel: fix some arm warnings
	. turn of fatal warnings for texinfo

Change-Id: I71e228c87a7226adbbd940ccb1439e042d7b6e9a