In older distros we were not including our copies of unistd_{32,64}.h,
as we were relying on the system's asm/unistd.h, and a log time ago
the files to be included were asm-{x86_64,i386}/unistd.h.

Fix it by also carrying a copy of asm/unistd.h, that will be the same
as in modern distros and will allow us to provide missing __NR_setns,
for instance, in older distros.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-iwmgm0c4m1ynstktzmkjh8di@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

We will need it to build tools/perf/trace/beauty/statx.h.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-nin41ve2fa63lrfbdr6x57yr@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

To make it nicer and easily maintainable.

Also moving the check into fixdep sub make, so its output is not
scattered around the build output.

Removing extra $$ from mman*.h checks.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Tested-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1481030331-31944-5-git-send-email-jolsa@kernel.org
[ Use /bin/sh, and 'function check() {' -> 'check () {' to make it work with busybox, in Alpine Linux, for instance ]
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>