fxsdk: add build-fxg3a -s (send) option

Note that this only makes sense if there is only one .g3a in the current
folder. If both the cg and the fxg3a targets are used, this will send
both g3a files, which is a waste of time.

fxsdk/fxsdk.sh

@@ -285,6 +285,10 @@ fxsdk_send_cg-push() {
   fxlink -pw ${bin_files}
 }
 
+fxsdk_send_fxg3a() {
+  fxsdk_send_cg "$@"
+}
+
 fxsdk_path() {
   case "$1" in
     "sysroot")