Merge bitcoin/bitcoin#24650: build: require libtool 2.4.2

061accf build: require libtool 2.4.2 (fanquake)

Pull request description:

  Every system we support has 2.4.6 available, except for OpenBSD, which
  [currently ships with 2.4.2](https://github.com/openbsd/ports/blob/master/devel/libtool/Makefile) (released 2011). For now, set our minimum
  required version to that.

  After a 7 year hitus, 2.4.7 has also very recently been released:
  https://savannah.gnu.org/forum/forum.php?forum_id=10139.

  Partially motivated by comments in bitcoin/bitcoin#24615.

  See also: https://repology.org/project/libtool/versions

ACKs for top commit:
  achow101:
    ACK 061accf
  hebasto:
    ACK 061accf
  prusnak:
    ACK 061accf

Tree-SHA512: bc032022b8609b73253ff1c4fd480f4d09be761b8fec295f39319f9499ee2df116f55295da476be551c43ed88fbb0bfed7bb5a188b9979b34147fe39737ec76f

Author: fanquake

configure.ac

@@ -96,10 +96,8 @@ fi
 AC_PROG_OBJCXX
 ])
 
-dnl Since libtool 1.5.2 (released 2004-01-25), on Linux libtool no longer
-dnl sets RPATH for any directories in the dynamic linker search path.
-dnl See more: https://wiki.debian.org/RpathIssue
-LT_PREREQ([1.5.2])
+dnl OpenBSD ships with 2.4.2
+LT_PREREQ([2.4.2])
 dnl Libtool init checks.
 LT_INIT([pic-only win32-dll])