CMake: Add DbgHelp define for MinGW

CMakeLists.txt

@@ -80,6 +80,7 @@ endif (UNIX)
 if (MINGW)
     find_package(Demangle)
     find_package(BFD)
+    find_package(DbgHelp)
 endif (MINGW)
 
 find_package(SSE)

cmake/FindDbgHelp.cmake

@@ -0,0 +1,20 @@
+include(CheckCXXSourceCompiles)
+
+check_cxx_source_compiles("
+    #include <windows.h>
+    #include <dbghelp.h>
+    int main() {
+        STACKFRAME64 frame;
+        IMAGEHLP_SYMBOL64 *sym_info;
+        IMAGEHLP_MODULE64 module;
+        IMAGEHLP_LINE64 line;
+        return 0;
+    }"
+    DBGHELP_FOUND
+)
+
+if (DBGHELP_FOUND)
+    add_compile_options(
+        -DWITH_DBGHELP
+    )
+endif (DBGHELP_FOUND)