Hello libtool devs,

There's a common information/warning message that occurs with building
secp256k1 for example where it states:

*"/usr/bin/ar: `u' modifier ignored since `D' is the default (see `U')"*

This can be resolved if "cru" is changed to "crU" in:

*/usr/share/aclocal/libtool.m4*


Please consider doing this, thank you !