Add MSYS2 UCRT64 compiler diagnostic scripts

check_cc.bat

@@ -0,0 +1,34 @@
+@echo off
+setlocal
+pushd "%~dp0"
+if errorlevel 1 (
+    echo [ERROR] Cannot open the script directory.
+    pause
+    exit /b 1
+)
+
+set "MSYS2_PATH=C:\msys64"
+if not "%MSYS2_ROOT%"=="" set "MSYS2_PATH=%MSYS2_ROOT%"
+if not "%MSYS2%"=="" set "MSYS2_PATH=%MSYS2%"
+set "PROBE_LOG=%CD%\cc-probe.log"
+set "PROBE_RESULT=1"
+
+> "%PROBE_LOG%" echo [INFO] MSYS2: %MSYS2_PATH%
+if not exist "%MSYS2_PATH%\msys2_shell.cmd" (
+    >> "%PROBE_LOG%" echo [ERROR] msys2_shell.cmd not found. Set MSYS2_ROOT to the MSYS2 directory.
+    goto finish
+)
+
+echo [INFO] Checking the UCRT64 C compiler...
+call "%MSYS2_PATH%\msys2_shell.cmd" -ucrt64 -here -defterm -no-start -c "bash ./check_cc.sh" >> "%PROBE_LOG%" 2>&1
+set "PROBE_RESULT=%ERRORLEVEL%"
+
+:finish
+>> "%PROBE_LOG%" echo [INFO] MSYS2 shell exit code: %PROBE_RESULT%
+type "%PROBE_LOG%"
+echo.
+echo [INFO] Log: "%PROBE_LOG%"
+if not "%PROBE_RESULT%"=="0" echo [ERROR] Compiler check failed. See the log above.
+if /i not "%~1"=="--no-pause" pause
+popd
+exit /b %PROBE_RESULT%

check_cc.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+set -uo pipefail
+
+# Проверяем компилятор отдельно от CMake и исходников проекта.
+probe_cc="${UTUN_PROBE_CC:-/ucrt64/bin/cc.exe}"
+printf '[INFO] MSYSTEM=%s\n[INFO] PATH=%s\n[INFO] Compiler=%s\n' "${MSYSTEM:-unset}" "$PATH" "$probe_cc"
+if [ ! -x "$probe_cc" ]; then
+    printf '[ERROR] Compiler is missing or not executable: %s\n' "$probe_cc"
+    exit 1
+fi
+
+probe_dir=$(mktemp -d "${TMPDIR:-/tmp}/utun-cc-probe.XXXXXX") || {
+    printf '[ERROR] Cannot create the temporary probe directory.\n'
+    exit 1
+}
+trap 'rm -rf -- "$probe_dir" || printf "[WARN] Cannot remove probe directory: %s\n" "$probe_dir"' EXIT
+printf '[INFO] Temporary directory: %s\n' "$probe_dir"
+
+# Каждый этап сохраняет собственный код завершения, включая молчаливые сбои.
+probe_step() {
+    local step="$1" result
+    shift
+    printf '\n[INFO] %s\n[INFO] Command:' "$step"
+    printf ' %q' "$@"
+    printf '\n'
+    "$@"
+    result=$?
+    printf '[INFO] %s exit code: %d\n' "$step" "$result"
+    if [ "$result" -ne 0 ]; then
+        printf '[ERROR] Failed stage: %s\n' "$step"
+    fi
+    return "$result"
+}
+
+printf '#include <stdio.h>\nint main(void) { puts("utun compiler probe OK"); return 0; }\n' > "$probe_dir/probe.c" || {
+    printf '[ERROR] Cannot write the probe source: %s/probe.c\n' "$probe_dir"
+    exit 1
+}
+probe_step 'Compiler version' "$probe_cc" --version || exit $?
+probe_step 'Compile' "$probe_cc" -v -std=c99 -c "$probe_dir/probe.c" -o "$probe_dir/probe.o" || exit $?
+probe_step 'Link' "$probe_cc" -v "$probe_dir/probe.o" -o "$probe_dir/probe.exe" || exit $?
+probe_step 'Run' "$probe_dir/probe.exe" || exit $?
+printf '\n[SUCCESS] Compile, link and run completed.\n'