ci: protect test.c with #if LV_BUILD_TEST

tests/makefile/Makefile

@@ -2,7 +2,7 @@ LVGL_DIR := $(CURDIR)/../..
 include ../../lvgl.mk
 
 CSRCS += test.c
-CFLAGS += -DLV_CONF_SKIP=1 -I$(LVGL_DIR)/..
+CFLAGS += -DLV_CONF_SKIP=1 -DLV_BUILD_TEST=1 -I$(LVGL_DIR)/..
 COBJS := $(patsubst %.c, %.o, $(CSRCS))
 
 test_file: $(COBJS)

tests/makefile/test.c

@@ -1,3 +1,4 @@
+#if LV_BUILD_TEST
 #include <stdio.h>
 #include "lvgl/lvgl.h"
 
@@ -5,3 +6,4 @@ int main(void) {
     lv_init();
     return 0;
 }
+#endif