selftests/bpf: Add uprobe_multi to gen_tar target

The uprobe_multi program was not picked up for the gen_tar target. Fix
by adding it to TEST_GEN_FILES.

Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20231004122721.54525-4-bjorn@kernel.org

Author: bjorn-rivos

tools/testing/selftests/bpf/Makefile

@@ -104,7 +104,7 @@ TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
 	xskxceiver xdp_redirect_multi xdp_synproxy veristat xdp_hw_metadata \
 	xdp_features
 
-TEST_GEN_FILES += liburandom_read.so urandom_read sign-file
+TEST_GEN_FILES += liburandom_read.so urandom_read sign-file uprobe_multi
 
 # Emit succinct information message describing current building step
 # $1 - generic step name (e.g., CC, LINK, etc);