Completely untested, but have you tried:
pkglib_LTLIBRARIES = noinst_LTLIBRARIES = if INSTALL_LIBS pkglib_LTLIBRARIES += $(LIBLIST) else noinst_LTLIBRARIES += $(LIBLIST) endif
Just tried it, same results, automake reports each module in LIBLIST as "already going to be installed in 'noinst'". In fact, I even tried changing noinst_ to lib_, and now it reports "already going to be installed in 'lib'".
