build: add ability to disable some plugins from packaging and tests

When custom-packaging the VPP artifacts, it can be useful to exclude
some of the core plugins from packaging/testing, for some reasons.
A removal of a plugin(s) from the worktree needs to be tracked as
a separate change, and thus is tricky from the maintenance
point of view.

This change adds the ability to "pretend they do not exist" -
plugins which are added to the comma-separated environment
variable "VPP_EXCLUDED_PLUGINS" will not be added to the build
process and not packaged.

The tests do not have the 1:1 relationship as plugins,
so they might need to be modified separately. This change
includes some of these modifications as an example.

Type: feature
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>
Change-Id: Id31562d00a01ced1acbb4996a633517cbd6f09d8
diff --git a/build-data/packages/vpp.mk b/build-data/packages/vpp.mk
index ad1d1fc..40aa8c7 100644
--- a/build-data/packages/vpp.mk
+++ b/build-data/packages/vpp.mk
@@ -30,6 +30,9 @@
 ifeq ("$(V)","1")
 vpp_cmake_args += -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON
 endif
+ifneq ($(VPP_EXCLUDED_PLUGINS),)
+vpp_cmake_args += -DVPP_EXCLUDED_PLUGINS="$(VPP_EXCLUDED_PLUGINS)"
+endif
 
 ifneq ($(VPP_EXTRA_CMAKE_ARGS),)
 vpp_cmake_args += $(VPP_EXTRA_CMAKE_ARGS)