autoconf: Rely on ar supporting index creation

autoconf: Rely on ar supporting index creation

This way we don't need RANLIB anymore, making it a bit simpler for the meson
build to generate Makefile.global for PGXS compatibility.

FreeBSD, NetBSD, OpenBSD, the only platforms where we didn't use AROPT=crs,
all have supported the 's' option for a long time.

On macOS we ran ranlib after installing a static library. This was added a
long time ago, in 58ad65ec2def. I cannot reproduce an issue in more recent
macOS versions. This is removed now.

Based on discussion with Tom, I left the 'touch' at the end of static
libraries generation, added in 826eff57c4c, in place. While it looks like
current versions of Apple's ar/ranlib don't need it, it was needed not too
long ago.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20221005200710.luvw5evhwf6clig6@awork3.anarazel.de