qemu-barrier: Fix compilation on i386 hosts Commit 610b823ef66b993660f1ab1447a769f190e4f3b3 uses QEMU_GNUC_PREREQ on i386 hosts. That macro is defined in qemu-common.h which is not always included before qemu-barrier.h, so compilation on i386 hosts was broken. Signed-off-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>