Disable ZXing size optimization for MinGW GCC string link issue

tools/chatgui/zxing-cpp/core/CMakeLists.txt

@@ -677,7 +677,10 @@ if (NOT ZXING_DISABLE_PCH)
     target_precompile_headers(ZXing PRIVATE ${PRECOMPILE_HEADERS})
 endif()
 
-if(CMAKE_BUILD_TYPE MATCHES "Release|RelWithDebInfo")
+# MinGW GCC с -Os даёт ошибку линковки move-конструктора std::string (MSYS2 #31015).
+if(MINGW AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    message(STATUS "ZXing: per-source -Os disabled for MinGW GCC (MSYS2 #31015)")
+elseif(CMAKE_BUILD_TYPE MATCHES "Release|RelWithDebInfo")
     # The following is a list of translation units that fulfill two criteria regarding the use of -Os vs -O3:
     #  1. their binary size decreases significantly
     #  2. the runtime of ReaderTest is not (measurably) affected