mk: fix USE_OPENSSL expand once
@@ -449,7 +449,7 @@ CFLAGS += -I$(OPENSSL_OPT)/include
LFLAGS += -L$(OPENSSL_OPT)/lib
endif
-USE_OPENSSL = $(shell $(call CC_TEST,openssl/ssl.h))
+USE_OPENSSL := $(shell $(call CC_TEST,openssl/ssl.h))
ifneq ($(USE_OPENSSL),)
CFLAGS += -DUSE_OPENSSL -DUSE_TLS
