Merge bitcoin/bitcoin#25282: Bugfix: configure: Define default for use_libevent

f0f5cd7 Bugfix: configure: Define default for use_libevent (Luke Dashjr)

Pull request description:

  Another trivial fix like #25051 - I think this is the only other one missing.

ACKs for top commit:
  laanwj:
    Code review ACK f0f5cd7

Tree-SHA512: 888c2e6d032ef1de5af635e2a9b2b8ab560c86bd10a6cee54aa9aa62ae43f03c19889bb6a2b64cf8982d4cd514f97ca3ed743c71ed0651e9295a4b1726955b9b

Author: laanwj

configure.ac

@@ -1554,6 +1554,7 @@ fi
 
 dnl libevent check
 
+use_libevent=no
 if test "$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench" != "nonononono"; then
   PKG_CHECK_MODULES([EVENT], [libevent >= 2.1.8], [use_libevent=yes], [AC_MSG_ERROR([libevent version 2.1.8 or greater not found.])])
   if test "$TARGET_OS" != "windows"; then