Link against libdl to enable use of dlopen etc in libcrypto.a

Makefile.linux

@@ -2,15 +2,16 @@ CC=gcc
 CXX=g++
 
 INCLUDES=-Iext/bin/libcrypto/include -Iext/jsoncpp/include
+LDFLAGS=-ldl
 ARCH=$(shell uname -m)
 DEFS=-DZT_ARCH="$(ARCH)" -DZT_OSNAME="linux" -DZT_TRACE
 
 # Uncomment for a release optimized build
-CFLAGS=-Wall -O3 -fno-unroll-loops -fstack-protector -pthread $(INCLUDES) -DNDEBUG $(DEFS)
+CFLAGS=-Wall -O3 -fno-unroll-loops -fstack-protector -pthread $(INCLUDES) $(LDFLAGS) -DNDEBUG $(DEFS)
 STRIP=strip --strip-all
 
 # Uncomment for a debug build
-#CFLAGS=-Wall -g -pthread $(INCLUDES) -DZT_TRACE -DZT_LOG_STDOUT $(DEFS)
+#CFLAGS=-Wall -g -pthread $(INCLUDES) $(LDFLAGS) -DZT_TRACE -DZT_LOG_STDOUT $(DEFS)
 #STRIP=echo
 
 CXXFLAGS=$(CFLAGS) -fno-rtti