Fix update-doxygen (again)

Bash trickery to find the script directory did not work, but we can just use
"trunk/tools" since trunk gets checked out into $DOXYGEN_TEMPDIR.
Review URL: https://codereview.appspot.com/6573055

git-svn-id: http://skia.googlecode.com/svn/trunk@5696 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/update-doxygen.sh b/tools/update-doxygen.sh
index f573fd7..5351659 100755
--- a/tools/update-doxygen.sh
+++ b/tools/update-doxygen.sh
@@ -31,8 +31,7 @@
 else
   svn checkout https://skia-autogen.googlecode.com/svn/docs  # writeable
 if [ ! -f "docs/static_footer.txt" ]; then
-  TOOLS_DIR="$(cd "$(dirname "$0" )" && pwd )"
-  cp ${TOOLS_DIR}/doxygen_footer.txt docs/static_footer.txt
+  cp trunk/tools/doxygen_footer.txt docs/static_footer.txt
 fi
 fi