virtiofsd: support nanosecond resolution for file timestamp

Define HAVE_STRUCT_STAT_ST_ATIM to 1 if `st_atim' is member of `struct
stat' which means support nanosecond resolution for the file timestamp
fields.

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

configure

@@ -5197,6 +5197,19 @@ if compile_prog "" "" ; then
     strchrnul=yes
 fi
 
+#########################################
+# check if we have st_atim
+
+st_atim=no
+cat > $TMPC << EOF
+#include <sys/stat.h>
+#include <stddef.h>
+int main(void) { return offsetof(struct stat, st_atim); }
+EOF
+if compile_prog "" "" ; then
+    st_atim=yes
+fi
+
 ##########################################
 # check if trace backend exists
 
@@ -6895,6 +6908,9 @@ fi
 if test "$strchrnul" = "yes" ; then
   echo "HAVE_STRCHRNUL=y" >> $config_host_mak
 fi
+if test "$st_atim" = "yes" ; then
+  echo "HAVE_STRUCT_STAT_ST_ATIM=y" >> $config_host_mak
+fi
 if test "$byteswap_h" = "yes" ; then
   echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
 fi

tools/virtiofsd/fuse_misc.h

@@ -7,6 +7,7 @@
  */
 
 #include <pthread.h>
+#include "config-host.h"
 
 /*
  * Versioned symbols cannot be used in some cases because it