libctf: try several possibilities for linker versioning flags

libctf: try several possibilities for linker versioning flags

Checking for linker versioning by just grepping ld --help output for
mentions of --version-script is inadequate now that Solaris 11.4
implements a --version-script with different semantics.  Try linking a
test program with a small wildcard-using version script with each
supported set of flags in turn, to make sure that linker versioning is
not only advertised but actually works.

The Solaris "GNU-compatible" linker versioning is not quite
GNU-compatible enough, but we can work around the differences by
generating a new version script that removes the comments from the
original (Solaris ld requires #-style comments), and making another
version script for libctf-nonbfd in particular which doesn't mention any
of the symbols that appear in libctf.la, to avoid Solaris ld introducing
corresponding new NOTYPE symbols to match the version script.

libctf/ChangeLog
2021-09-27  Nick Alcock  <nick.alcock@oracle.com>

	PR libctf/27967
	* configure.ac (VERSION_FLAGS): Replace with...
	(ac_cv_libctf_version_script): ... this multiple test.
	(VERSION_FLAGS_NOBFD): Substitute this too.
	* Makefile.am (libctf_nobfd_la_LDFLAGS): Use it.  Split out...
	(libctf_ldflags_nover): ... non-versioning flags here.
	(libctf_la_LDFLAGS): Use it.
	* libctf.ver: Give every symbol not in libctf-nobfd a comment on
	the same line noting as much.