Partial reversion of af57525d

The issue is that `COMMANDLINE_LIBRARY` is used by EPICS base to link against
some other libraries; removing this line means that every lib*.so now links
against libreadline.so. This isn't _strictly speaking_ an issue because
`softIocPVA` also ultimately depends on libreadline. However, it is bad
practice.

require-ess/tools/driver.makefile

@@ -192,6 +192,8 @@ USR_CPPFLAGS+=-DUSE_TYPED_RSET
 endif
 
 SHRLIB_VERSION=
+# Avoid linking everything with libreadline.so
+COMMANDLINE_LIBRARY=
 
 OBJ=.o