BUILD: makefile: search for SSL_INC/wolfssl before SSL_INC

Building with an install of wolfssl and openssl side-by-side breaks
because for wolfssl we need the two include levels and since some
names are in common, this results in some files being found in the
original openssl tree. Let's swap the two include paths so that all
that is related to wolfssl is found there first when needed.

No backport is needed.
diff --git a/Makefile b/Makefile
index c66fb45..3b1ff10 100644
--- a/Makefile
+++ b/Makefile
@@ -574,7 +574,7 @@
 # This is for the WolfSSL variant of the OpenSSL API. Setting it implies
 # OPENSSL so it's not necessary to set the latter.
 ifneq ($(USE_OPENSSL_WOLFSSL),)
-  SSL_CFLAGS      := $(if $(SSL_INC),-I$(SSL_INC) -I$(SSL_INC)/wolfssl)
+  SSL_CFLAGS      := $(if $(SSL_INC),-I$(SSL_INC)/wolfssl -I$(SSL_INC))
   SSL_LDFLAGS     := $(if $(SSL_LIB),-L$(SSL_LIB)) -lwolfssl
   # always automatically set USE_OPENSSL
   USE_OPENSSL     := $(if $(USE_OPENSSL),$(USE_OPENSSL),implicit)