Fix printf usage in _wrap_build()

On some systems using floating-point instead of decimal results
in the build time being displayed as "nan:nan".

Test: m, "build completed successfully (02:26 (mm:ss))"
Change-Id: I7a2b401903b63117a7718cc5aa2a0d5610b57ca2

shell_utils.sh

@@ -114,11 +114,11 @@ function _wrap_build()
         echo -n "${color_failed}#### failed to build some targets "
     fi
     if [ $hours -gt 0 ] ; then
-        printf "(%02g:%02g:%02g (hh:mm:ss))" $hours $mins $secs
+        printf "(%02d:%02d:%02d (hh:mm:ss))" $hours $mins $secs
     elif [ $mins -gt 0 ] ; then
-        printf "(%02g:%02g (mm:ss))" $mins $secs
+        printf "(%02d:%02d (mm:ss))" $mins $secs
     elif [ $secs -gt 0 ] ; then
-        printf "(%s seconds)" $secs
+        printf "(%d seconds)" $secs
     fi
     echo " ####${color_reset}"
     echo