Fix --without-cxx-binding being ignored

Do not build the C++ bindings if the configure script was called
with the option --without-cxx-binding.

c++/Makefile.am

@@ -1,3 +1,4 @@
+if ENABLE_CXX
 
 lib_LTLIBRARIES = libhamlib++.la
 libhamlib___la_SOURCES = rigclass.cc rotclass.cc ampclass.cc
@@ -15,3 +16,5 @@ TESTS = $(check_PROGRAMS)
 
 $(top_builddir)/src/libhamlib.la:
 	$(MAKE) -C $(top_builddir)/src/ libhamlib.la
+
+endif

configure.ac

@@ -560,6 +560,7 @@ AC_MSG_RESULT([$cf_with_cxx_binding])
 AS_IF([test x"${cf_with_cxx_binding}" = "xyes"],
       [BINDINGS="${BINDINGS} c++"])
 
+AM_CONDITIONAL([ENABLE_CXX], [test x"${cf_with_cxx_binding}" = "xyes"])
 
 dnl Check if perl-binding is wanted, default is to not build it