webkit: Add --enable-dependency-tracking to the configure options

--disable-dependency-tracking was added globally to
package/pkg-autotools.mk by this commit:

http://git.buildroot.net/buildroot/commit/?id=3e37b0fc6cbbe2245e39fedb247a381fb4e0d992

This causes a failure in webkit because some source files are generated
after the Makefile is created. To fix this, we add
--enable-dependency-tracking to the configure options.

Fixes:
  http://autobuild.buildroot.net/results/5beea967b02df202bca1d42afd6fa8c2c13383d5/



Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>