Merge bitcoin#19565: build: call AC_PATH_TOOL for dsymutil in macOS cross-compile

ef3d4ce build: call AC_PATH_TOOL for dsymutil in macOS cross-compile (fanquake)

Pull request description:

  While testing bitcoin#19530 I noticed that we couldn't call [`dsymutil`](https://www.llvm.org/docs/CommandGuide/dsymutil.html) after LTO:
  ```bash
  ../libtool: line 10643: x86_64-apple-darwin16-dsymutil: command not found
  ```

  This updates configure to call `AC_PATH_TOOL` so that we end up with the
  full path to dsymutil, similar to `otool` and `install_name_tool`, ie:
  `/bitcoin/depends/x86_64-apple-darwin16/share/../native/bin/x86_64-apple-darwin16-dsymutil`.

ACKs for top commit:
  laanwj:
    Code review ACK ef3d4ce
  theuni:
    ACK ef3d4ce.

Tree-SHA512: e4fa93e7f9f7945289143dfe2a6645ad8ee7f3bee0793412b3509901a30566d6f952e3b39e0e525a54f8dbd0c480f8da70fc6cb80b07800d11b0c6071fbb7466

Author: fanquake

configure.ac

@@ -631,6 +631,7 @@ case $host in
            BUILD_OS=darwin
            ;;
          *)
+           AC_PATH_TOOL([DSYMUTIL], [dsymutil], dsymutil)
            AC_PATH_TOOL([INSTALLNAMETOOL], [install_name_tool], install_name_tool)
            AC_PATH_TOOL([OTOOL], [otool], otool)
            AC_PATH_PROGS([GENISOIMAGE], [genisoimage mkisofs],genisoimage)