Merge bitcoin/bitcoin#23557: configure.ac: remove Bashism

cf72925 configure.ac: remove Bashism (Matt Whitlock)

Pull request description:

  Configure scripts are supposed to adhere to the POSIX shell language. The POSIX `test` builtin does not implement an `==` operator. Bash does, but not all systems have Bash installed as `/bin/sh`. In particular, many systems use the lighter-weight Dash as the default POSIX shell. Dash emits the following error when running `configure`:

  ```
  ./configure: 39065: test: xno: unexpected operator
  ```

  This PR removes the Bashism and restores correct operation with POSIX-compliant shells like Dash.

ACKs for top commit:
  katesalazar:
    ACK cf72925.
  laanwj:
    Code review ACK cf72925

Tree-SHA512: 578c873fba52e0472baed9e024bddcf58a0e088600bd5854f3011f1f8d135773ad923bb16baefc960d17ecedee9cc980b36aaa70fb32eb9bc7de93f7fe60541d

Author: MarcoFalke

configure.ac

@@ -1923,7 +1923,7 @@ if test x$bitcoin_enable_qt != xno; then
     echo "    with qr       = $use_qr"
 fi
 echo "  with zmq        = $use_zmq"
-if test x$enable_fuzz == xno; then
+if test x$enable_fuzz = xno; then
     echo "  with test       = $use_tests"
 else
     echo "  with test       = not building test_bitcoin because fuzzing is enabled"