getloadavg is supported on Linux, BSDs, Solaris.

Following man page:
RETURN VALUE
       If the load average was unobtainable, -1 is returned; otherwise,
       the number of samples actually retrieved is returned.

accordingly, make stub for systems which don't support this function return -1
for consistency.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/qemu/osdep.h | 10 ++++++++++
 meson.build          |  1 +
 2 files changed, 11 insertions(+)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 475a1c62ff..d30ba73eda 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -779,6 +779,16 @@ static inline int platform_does_not_support_system(const char *command)
 }
 #endif /* !HAVE_SYSTEM_FUNCTION */
 
+/**
+ * If the load average was unobtainable, -1 is returned
+ */
+#ifndef HAVE_GETLOADAVG_FUNCTION
+static inline int getloadavg(double loadavg[], int nelem)
+{
+    return -1;
+}
+#endif /* !HAVE_GETLOADAVG_FUNCTION */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/meson.build b/meson.build
index ec01f8b138..d2c4c2adb3 100644
--- a/meson.build
+++ b/meson.build
@@ -2293,6 +2293,7 @@ config_host_data.set('HAVE_GLIB_WITH_SLICE_ALLOCATOR', glib_has_gslice)
 config_host_data.set('HAVE_OPENPTY', cc.has_function('openpty', dependencies: util))
 config_host_data.set('HAVE_STRCHRNUL', cc.has_function('strchrnul'))
 config_host_data.set('HAVE_SYSTEM_FUNCTION', cc.has_function('system', prefix: '#include <stdlib.h>'))
+config_host_data.set('HAVE_GETLOADAVG_FUNCTION', cc.has_function('getloadavg', prefix: '#include <stdlib.h>'))
 if rbd.found()
   config_host_data.set('HAVE_RBD_NAMESPACE_EXISTS',
                        cc.has_function('rbd_namespace_exists',
-- 
MST