meson: Use has_header_symbol() to check getcpu()

meson: Use has_header_symbol() to check getcpu()

The use of gnu_source_prefix in the detection of getcpu() was
ineffective because the header file that declares getcpu() when
_GNU_SOURCE is defined was not included. Pass sched.h to
has_header_symbol() so that the existence of the declaration will be
properly checked.

Cc: qemu-stable@nongnu.org
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250424-buildsys-v1-1-97655e3b25d7@daynix.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit 563cd698dffb977eea0ccfef3b95f6f9786766f3)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>