osdep.h: Remove <sys/signal.h> include

Prior to 2a4b472, sys/signal.h was only included on OpenBSD
(apart from two .c files). The POSIX standard location for this
header is just <signal.h> and in fact, OpenBSD's signal.h includes
sys/signal.h itself.

Unconditionally including <sys/signal.h> on musl causes warnings
for just about every source file:

  /usr/include/sys/signal.h:1:2: warning: #warning redirecting incorrect #include <sys/signal.h> to <signal.h> [-Wcpp]
      1 | #warning redirecting incorrect #include <sys/signal.h> to <signal.h>
        |  ^~~~~~~

Since there don't seem to be any platforms which require including
<sys/signal.h> in addition to <signal.h>, and some platforms like
Haiku lack it completely, just remove it.

Tested building on OpenBSD after removing this include.

Signed-off-by: Michael Forney <mforney@mforney.org>
Tested-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210113215600.16100-1-mforney@mforney.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

include/qemu/osdep.h

@@ -104,10 +104,6 @@ extern int daemon(int, int);
 #include <setjmp.h>
 #include <signal.h>
 
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h>
-#endif
-
 #ifndef _WIN32
 #include <sys/wait.h>
 #else

meson.build

@@ -1113,7 +1113,6 @@ config_host_data.set('HAVE_DRM_H', cc.has_header('libdrm/drm.h'))
 config_host_data.set('HAVE_PTY_H', cc.has_header('pty.h'))
 config_host_data.set('HAVE_SYS_IOCCOM_H', cc.has_header('sys/ioccom.h'))
 config_host_data.set('HAVE_SYS_KCOV_H', cc.has_header('sys/kcov.h'))
-config_host_data.set('HAVE_SYS_SIGNAL_H', cc.has_header('sys/signal.h'))
 
 ignored = ['CONFIG_QEMU_INTERP_PREFIX'] # actually per-target
 arrays = ['CONFIG_AUDIO_DRIVERS', 'CONFIG_BDRV_RW_WHITELIST', 'CONFIG_BDRV_RO_WHITELIST']