[PATCH v3 08/11] xfsprogs: Add fls check into autoconf

[Christoph Hellwig]

Can't you just use something like:

AC_CHECK_DECL([fls],
        [AC_DEFINE([HAVE_FLS_PROTOTYPE], [1],
	 [Define to 1 if have fls prototype])],
	 [],
	 [#include <string.h>])