selftests/bpf: structure test_{progs, maps, verifier} test runners uniformly

It's easier to follow the logic if it's structured the same.
There is just slight difference between test_progs/test_maps and
test_verifier. test_verifier's verifier/*.c files are not really compilable
C files (they are more of include headers), so they can't be specified as
explicit dependencies of test_verifier.

Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/Makefile

@@ -176,6 +176,7 @@ endif
 endif
 
 TEST_PROGS_CFLAGS := -I. -I$(OUTPUT)
+TEST_MAPS_CFLAGS := -I. -I$(OUTPUT)
 TEST_VERIFIER_CFLAGS := -I. -I$(OUTPUT) -Iverifier
 
 ifneq ($(SUBREG_CODEGEN),)
@@ -227,16 +228,14 @@ ifeq ($(DWARF2BTF),y)
 	$(BTF_PAHOLE) -J $@
 endif
 
-PROG_TESTS_H := $(OUTPUT)/prog_tests/tests.h
-test_progs.c: $(PROG_TESTS_H)
-$(OUTPUT)/test_progs: CFLAGS += $(TEST_PROGS_CFLAGS)
-$(OUTPUT)/test_progs: prog_tests/*.c
-
 PROG_TESTS_DIR = $(OUTPUT)/prog_tests
 $(PROG_TESTS_DIR):
 	mkdir -p $@
-
+PROG_TESTS_H := $(PROG_TESTS_DIR)/tests.h
 PROG_TESTS_FILES := $(wildcard prog_tests/*.c)
+test_progs.c: $(PROG_TESTS_H)
+$(OUTPUT)/test_progs: CFLAGS += $(TEST_PROGS_CFLAGS)
+$(OUTPUT)/test_progs: test_progs.c $(PROG_TESTS_H) $(PROG_TESTS_FILES)
 $(PROG_TESTS_H): $(PROG_TESTS_FILES) | $(PROG_TESTS_DIR)
 	$(shell ( cd prog_tests/; \
 		  echo '/* Generated header, do not edit */'; \
@@ -250,7 +249,6 @@ $(PROG_TESTS_H): $(PROG_TESTS_FILES) | $(PROG_TESTS_DIR)
 		  echo '#endif' \
 		 ) > $(PROG_TESTS_H))
 
-TEST_MAPS_CFLAGS := -I. -I$(OUTPUT)
 MAP_TESTS_DIR = $(OUTPUT)/map_tests
 $(MAP_TESTS_DIR):
 	mkdir -p $@
@@ -272,17 +270,15 @@ $(MAP_TESTS_H): $(MAP_TESTS_FILES) | $(MAP_TESTS_DIR)
 		  echo '#endif' \
 		 ) > $(MAP_TESTS_H))
 
-VERIFIER_TESTS_H := $(OUTPUT)/verifier/tests.h
-test_verifier.c: $(VERIFIER_TESTS_H)
-$(OUTPUT)/test_verifier: CFLAGS += $(TEST_VERIFIER_CFLAGS)
-$(OUTPUT)/test_verifier: test_verifier.c $(VERIFIER_TESTS_H)
-
 VERIFIER_TESTS_DIR = $(OUTPUT)/verifier
 $(VERIFIER_TESTS_DIR):
 	mkdir -p $@
-
+VERIFIER_TESTS_H := $(VERIFIER_TESTS_DIR)/tests.h
 VERIFIER_TEST_FILES := $(wildcard verifier/*.c)
-$(OUTPUT)/verifier/tests.h: $(VERIFIER_TEST_FILES) | $(VERIFIER_TESTS_DIR)
+test_verifier.c: $(VERIFIER_TESTS_H)
+$(OUTPUT)/test_verifier: CFLAGS += $(TEST_VERIFIER_CFLAGS)
+$(OUTPUT)/test_verifier: test_verifier.c $(VERIFIER_TESTS_H)
+$(VERIFIER_TESTS_H): $(VERIFIER_TEST_FILES) | $(VERIFIER_TESTS_DIR)
 	$(shell ( cd verifier/; \
 		  echo '/* Generated header, do not edit */'; \
 		  echo '#ifdef FILL_ARRAY'; \