main: use date/time/timezone as build string

Makefile

@@ -13,6 +13,7 @@ all: $(BUILD)/tbm
 -include scripts/Makefile.${TARGET}
 
 CFLAGS += -DTBM_VERSION=\"2017-10-31\"
+CFLAGS += -DBUILD_VERSION=\""$(shell date -u)"\"
 CFLAGS += -Iinclude
 CFLAGS += -Wall -Wextra -Wshadow -Wimplicit-function-declaration
 CFLAGS += -Wredundant-decls -pedantic

source/main.c

@@ -101,8 +101,8 @@ int main(void)
 		fprintf(admin_con->fp, "error: unable to probe flash chip.\n");
 	}
 
-	fprintf(user_con->fp, "TBM-dev (built on " __DATE__ ")\n");
-	fprintf(admin_con->fp, "TBM-dev (built on " __DATE__ ")\n");
+	fprintf(user_con->fp, "TBM-dev (built on " BUILD_VERSION ")\n");
+	fprintf(admin_con->fp, "TBM-dev (built on " BUILD_VERSION ")\n");
 
 	shell_init(&user_shell, user_cmds, user_con, "tbm $",
 		SHELL_SHOW_EXIT_CODE);