devtools: catch empty symbol maps

version.map are now optional for drivers if no symbol is exported.
Having no symbol exported from a library does not make sense.

Catch all empty maps and warn about them.

Example:
$ ./devtools/check-symbol-maps.sh
Found empty maps:
drivers/crypto/uadk/version.map
drivers/net/gve/version.map
drivers/net/idpf/version.map

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Tested-by: Ferruh Yigit <ferruh.yigit@amd.com>

devtools/check-symbol-maps.sh

@@ -60,4 +60,18 @@ if [ -n "$local_miss_maps" ] ; then
     ret=1
 fi
 
+find_empty_maps ()
+{
+    for map in $@ ; do
+        [ $(buildtools/map-list-symbol.sh $map | wc -l) != '0' ] || echo $map
+    done
+}
+
+empty_maps=$(find_empty_maps $@)
+if [ -n "$empty_maps" ] ; then
+    echo "Found empty maps:"
+    echo "$empty_maps"
+    ret=1
+fi
+
 exit $ret