BUG/BUILD: revert accidental change in the makefile from latest SSL fix

Commit 0bed994 ("BUG/MINOR: ssl: correctly initialize ssl ctx for
invalid certificates") accidently left a change in the Makefile
resulting in -ldl being appended to the LDFLAGS. As reported by
Dmitry Sivachenko, this will break build on systems without libdl
such as FreeBSD.

This fix must be backported to 1.5.
diff --git a/Makefile b/Makefile
index ee7473c..0d1d13a 100644
--- a/Makefile
+++ b/Makefile
@@ -540,7 +540,7 @@
 # in the usual path, use SSL_INC=/path/to/inc and SSL_LIB=/path/to/lib.
 BUILD_OPTIONS   += $(call ignore_implicit,USE_OPENSSL)
 OPTIONS_CFLAGS  += -DUSE_OPENSSL $(if $(SSL_INC),-I$(SSL_INC))
-OPTIONS_LDFLAGS += $(if $(SSL_LIB),-L$(SSL_LIB)) -lssl -lcrypto -ldl
+OPTIONS_LDFLAGS += $(if $(SSL_LIB),-L$(SSL_LIB)) -lssl -lcrypto
 OPTIONS_OBJS  += src/ssl_sock.o src/shctx.o
 ifneq ($(USE_PRIVATE_CACHE),)
 OPTIONS_CFLAGS  += -DUSE_PRIVATE_CACHE