Ended up using the same approach as libatomic, moving the checking logic into libgupc/configure.tgt.
+# Disable libgupc on unsupported systems. +if test -d ${srcdir}/libgupc; then + if test x$enable_libgupc = x; then + AC_MSG_CHECKING([for libgupc support]) + if (srcdir=${srcdir}/libgupc; \ + . ${srcdir}/configure.tgt; \ + test -n "$UNSUPPORTED") + then + AC_MSG_RESULT([no]) + noconfigdirs="$noconfigdirs target-libgupc" + else + AC_MSG_RESULT([yes]) + fi + fi +fi + Thanks, - Gary