Add -no-undefined to libtool invocation

The MinGW build will refuse to create a shared library unless explicitly
told that we are not going to build a broken one.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

Makefile.am

@@ -41,7 +41,7 @@ LT_VER_ARG = -version-info
 else
 LT_VER_ARG = -version-number
 endif
-libopenconnect_la_LDFLAGS = $(LT_VER_ARG) @APIMAJOR@:@APIMINOR@
+libopenconnect_la_LDFLAGS = $(LT_VER_ARG) @APIMAJOR@:@APIMINOR@ -no-undefined
 noinst_HEADERS = openconnect-internal.h openconnect.h gnutls.h
 include_HEADERS = openconnect.h
 if HAVE_SYMBOL_VERSIONING