When compiling without external signer support, the resulted `bench_bitcoin.exe` fails on Windows:
```
>.\bench_bitcoin.exe -filter=AddrManSelectByNetwork
Error: bad optional access
```

Steps to reproduce the failure:
- cross compiling on Ubuntu 22.04:
```
$ make -j $(nproc) -C depends HOST=x86_64-w64-mingw32 NO_QT=1
$ ./autogen.sh
$ ./configure CONFIG_SITE=$PWD/depends/x86_64-w64-mingw32/share/config.site --disable-external-signer
$ make -j $(nproc)
```
- compiling natively on Windows:

Apply the diff as follows:
```diff
--- a/build_msvc/bitcoin_config.h.in
+++ b/build_msvc/bitcoin_config.h.in
@@ -41,9 +41,6 @@
 /* Define this symbol to enable ZMQ functions */
 #define ENABLE_ZMQ 1
 
-/* define if external signer support is enabled (requires Boost::Process) */
-#define ENABLE_EXTERNAL_SIGNER /**/
-
 /* Define to 1 if you have the declaration of `be16toh', and to 0 if you
    don't. */
 #define HAVE_DECL_BE16TOH 0
```
Then
```
>py -3 build_msvc\msvc-autogen.py
>msbuild build_msvc\bitcoin.sln -property:Configuration=Release -verbosity:minimal
>src\bench_bitcoin.exe -filter=AddrManSelectByNetwork
Error: bad optional access
```

---

The failure does not manifest itself when running `bench_bitcoin.exe` using Wine on Linux.
{
    const std::array<unsigned char, 32> privkey_bytes = {
        // j
        // d
        0xD9, 0x7F, 0x51, 0x08, 0xF1, 0x1C, 0xDA, 0x6E,
        0xEE, 0xBA, 0xAA, 0x42, 0x0F, 0xEF, 0x07, 0x26,
        0xB1, 0xF8, 0x98, 0x06, 0x0B, 0x98, 0x48, 0x9F,
        0xA3, 0x09, 0x84, 0x63, 0xC0, 0x03, 0x28, 0x66
    };
    const std::string message = "Trust no one";
    const std::string expected_signature =
        "IPojfrX2dfPnH26UegfbGQQLrdK844DlHq5157/P6h57WyuS/Qsl+h/WSVGDF4MUi4rWSswW38oimDYfNNUBUOk=";
    CKey privkey;
    std::string generated_signature;
    BOOST_REQUIRE_MESSAGE(!privkey.IsValid(),
        "Confirm the private key is invalid");
    BOOST_CHECK_MESSAGE(!MessageSign(privkey, message, generated_signature),
        "Sign with an invalid private key");
    privkey.Set(privkey_bytes.begin(), privkey_bytes.end(), true);
    BOOST_REQUIRE_MESSAGE(privkey.IsValid(),
        "Confirm the private key is valid");
    BOOST_CHECK_MESSAGE(MessageSign(privkey, message, generated_signature),
        "Sign with a valid private key");
    BOOST_CHECK_EQUAL(expected_signature, generated_signature);
}
BOOST_AUTO_TEST_CASE(message_verify)