selftests: net: build net/lib dependency in all target

We have the logic to include net/lib automatically for net related
selftests. However, currently, this logic is only in install target
which means only `make install` will have net/lib included. This commit
adds the logic to all target so that all `make`, `make run_tests` and
`make install` will have net/lib included in net related selftests.

Signed-off-by: Bui Quang Minh <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Fixes: b86761ff6374 ("selftests: net: add scaffolding for Netlink tests in Python")
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/Makefile

···
 
 all:
 	@ret=1;							\
-	for TARGET in $(TARGETS); do				\
+	for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do	\
 		BUILD_TARGET=$$BUILD/$$TARGET;			\
 		mkdir $$BUILD_TARGET  -p;			\
 		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET	\