Make mmm handle symbolic links.

Use the PWD= /bin/pwd trick used in getopt in mmm so that it can deal with a symlinked
root directory.

Change-Id: Ia8b5ef10cbd10ca05f2301db86f64fdf11ff2840

envsetup.sh

@@ -625,7 +625,8 @@ function mmm()
             if [ -f $DIR/Android.mk ]; then
                 TO_CHOP=`echo $T | wc -c | tr -d ' '`
                 TO_CHOP=`expr $TO_CHOP + 1`
-                MFILE=`echo $PWD | cut -c${TO_CHOP}-`
+                START=`PWD= /bin/pwd`
+                MFILE=`echo $START | cut -c${TO_CHOP}-`
                 if [ "$MFILE" = "" ] ; then
                     MFILE=$DIR/Android.mk
                 else