Fix in tree build of openssl on mac
diff --git a/Makefile b/Makefile
index 0046a53..e00f969 100644
--- a/Makefile
+++ b/Makefile
@@ -292,8 +292,9 @@
ifeq ($(HAS_EMBEDDED_OPENSSL_ALPN),true)
OPENSSL_DEP = $(LIBDIR)/$(CONFIG)/openssl/libssl.a
OPENSSL_MERGE_LIBS += $(LIBDIR)/$(CONFIG)/openssl/libssl.a $(LIBDIR)/$(CONFIG)/openssl/libcrypto.a
-CPPFLAGS += -Ithird_party/openssl/include
-LDFLAGS += -L$(LIBDIR)/$(CONFIG)/openssl
+# need to prefix these to ensure overriding system libraries
+CPPFLAGS := -Ithird_party/openssl/include $(CPPFLAGS)
+LDFLAGS := -L$(LIBDIR)/$(CONFIG)/openssl $(LDFLAGS)
LIBS_SECURE = dl
else
NO_SECURE = true