Merge bitcoin/bitcoin#29868: Reintroduce external signer support for Windows

3a18075aed ci: Drop `-DENABLE_EXTERNAL_SIGNER=ON` configure option (Hennadii Stepanov)
719fa9f4ef build: Re-enable external signer support for Windows (Hennadii Stepanov)
6e5fc2bf9b test: Reintroduce Windows support in `system_tests/run_command` test (Hennadii Stepanov)

Pull request description:

  This PR partially reverts:
  - https://github.com/bitcoin/bitcoin/pull/28967
  - https://github.com/bitcoin/bitcoin/pull/29489

  After this PR, we can proceed to actually remove the [unused code](https://github.com/bitcoin/bitcoin/pull/28981#pullrequestreview-1991272752) from `src/util/subprocess.h`.

ACKs for top commit:
  Sjors:
    ACK 3a18075aed.
  theStack:
    Light ACK 3a18075aed
  laanwj:
    Code review and lightly tested ACK 3a18075aed

Tree-SHA512: 00d200685906e716750aae7cffa0794cca451653738ea590f50dfa28e1f3c5762a9be0ae0917aa0cf7436f00fe1e565236bff2853896530a5879466f7f45cb25

CMakeLists.txt

@@ -130,7 +130,7 @@ if(WITH_USDT)
   find_package(USDT MODULE REQUIRED)
 endif()
 
-cmake_dependent_option(ENABLE_EXTERNAL_SIGNER "Enable external signer support." ON "NOT WIN32" OFF)
+option(ENABLE_EXTERNAL_SIGNER "Enable external signer support." ON)
 
 cmake_dependent_option(WITH_QRENCODE "Enable QR code support." ON "BUILD_GUI" OFF)
 if(WITH_QRENCODE)

ci/test/03_test_script.sh

@@ -118,7 +118,7 @@ BASE_BUILD_DIR=${BASE_BUILD_DIR:-$BASE_SCRATCH_DIR/build-$HOST}
 mkdir -p "${BASE_BUILD_DIR}"
 cd "${BASE_BUILD_DIR}"
 
-BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DENABLE_EXTERNAL_SIGNER=ON -DCMAKE_INSTALL_PREFIX=$BASE_OUTDIR"
+BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DCMAKE_INSTALL_PREFIX=$BASE_OUTDIR"
 
 if [[ "${RUN_TIDY}" == "true" ]]; then
   BITCOIN_CONFIG_ALL="$BITCOIN_CONFIG_ALL -DCMAKE_EXPORT_COMPILE_COMMANDS=ON"

src/test/system_tests.cpp

@@ -25,7 +25,11 @@ BOOST_AUTO_TEST_CASE(run_command)
         BOOST_CHECK(result.isNull());
     }
     {
+#ifdef WIN32
+        const UniValue result = RunCommandParseJSON("cmd.exe /c echo {\"success\": true}");
+#else
         const UniValue result = RunCommandParseJSON("echo {\"success\": true}");
+#endif
         BOOST_CHECK(result.isObject());
         const UniValue& success = result.find_value("success");
         BOOST_CHECK(!success.isNull());
@@ -33,12 +37,20 @@ BOOST_AUTO_TEST_CASE(run_command)
     }
     {
         // An invalid command is handled by cpp-subprocess
+#ifdef WIN32
+        const std::string expected{"CreateProcess failed: "};
+#else
         const std::string expected{"execve failed: "};
+#endif
         BOOST_CHECK_EXCEPTION(RunCommandParseJSON("invalid_command"), subprocess::CalledProcessError, HasReason(expected));
     }
     {
         // Return non-zero exit code, no output to stderr
+#ifdef WIN32
+        const std::string command{"cmd.exe /c exit 1"};
+#else
         const std::string command{"false"};
+#endif
         BOOST_CHECK_EXCEPTION(RunCommandParseJSON(command), std::runtime_error, [&](const std::runtime_error& e) {
             const std::string what{e.what()};
             BOOST_CHECK(what.find(strprintf("RunCommandParseJSON error: process(%s) returned 1: \n", command)) != std::string::npos);
@@ -47,7 +59,11 @@ BOOST_AUTO_TEST_CASE(run_command)
     }
     {
         // Return non-zero exit code, with error message for stderr
+#ifdef WIN32
+        const std::string command{"cmd.exe /c \"echo err 1>&2 && exit 1\""};
+#else
         const std::string command{"sh -c 'echo err 1>&2 && false'"};
+#endif
         const std::string expected{"err"};
         BOOST_CHECK_EXCEPTION(RunCommandParseJSON(command), std::runtime_error, [&](const std::runtime_error& e) {
             const std::string what(e.what());
@@ -58,17 +74,23 @@ BOOST_AUTO_TEST_CASE(run_command)
     }
     {
         // Unable to parse JSON
+#ifdef WIN32
+        const std::string command{"cmd.exe /c echo {"};
+#else
         const std::string command{"echo {"};
+#endif
         BOOST_CHECK_EXCEPTION(RunCommandParseJSON(command), std::runtime_error, HasReason("Unable to parse JSON: {"));
     }
-    // Test std::in
+#ifndef WIN32
     {
+        // Test stdin
         const UniValue result = RunCommandParseJSON("cat", "{\"success\": true}");
         BOOST_CHECK(result.isObject());
         const UniValue& success = result.find_value("success");
         BOOST_CHECK(!success.isNull());
         BOOST_CHECK_EQUAL(success.get_bool(), true);
     }
+#endif
 }
 #endif // ENABLE_EXTERNAL_SIGNER