Run vpp-configure on change to cmake config files.

Run vpp-configure on change to cmake config files.

Modify the dirs assignment in configure_check_timestamp to
add the build-data/platforms/$(PLATFORM).mk file, all the CMakeLists.txt
files in the $(PACKAGE_SOURCE) tree, and the $(PACKAGE_SOURCE)/cmake
directory.
(For example, for package vpp, $(PACKAGE_SOURCE) is <Top of Tree>/src).
Note that in an earlier era there was no build-data/platforms directory and
no CMakeLists.txt files.
Also, we tacitly assume that $(SOURCE_PATH_BUILD_DATA_DIRS) is only one
directory whereas ebuild has been used in environments where there are two
treetops.

Change-Id: I761219adbdb4c7e675bb12b3e7f052db68f0294c
Signed-off-by: Burt Silverman <burtms@gmail.com>