[build] move dumpvar.mk include after select.mk include

because the dumpvar target was included early in envsetup.mk, it was
not possible to use it to dump variables that were defined by makefiles
included later (like the toolchain variables in combo/select.mk).

move dumpvar.mk to after select.mk and javac.mk, so that shell functions
can be created using the toolchain build variables

Change-Id: I1c22025a8981fa91c183846fb28be26fb562adfb
Signed-off-by: Gary King <gking@nvidia.com>