If VPP_EXTRA_CMAKE_ARGS is set, its content will be
appended to the vpp cmake command cli
Type: feature
Change-Id: I825d4239e62b0a2fb70a652f0671f6c559630aad
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
(cherry picked from commit 29736540335fb983f472457883e9fefde61bd913)