message: Implemented error handling for Windows build
diff: @@ -26,13 +26,13 @@ pushd "%BUILD_DIR%"
  %QTDIR%\bin\qmake.exe ^
  -spec win32-msvc ^
  "CONFIG += release" ^
  - "%SRC_DIR%\src.pro"
  + "%SRC_DIR%\src.pro" || goto :ERROR
  -nmake
  +nmake || goto :ERROR
  popd
  -%QTDIR%\bin\windeployqt "%OUT_DIR%\Spectrecoin.exe"
  +%QTDIR%\bin\windeployqt "%OUT_DIR%\Spectrecoin.exe" || goto :ERROR
  ::ren "%OUT_DIR%" Spectrecoin
  ::echo "The prepared package is in: %SRC_DIR%\Spectrecoin"
  @@ -40,6 +40,11 @@ popd
  echo "Everything is OK"
  GOTO END
  +:ERROR
  +echo Failed with error #%errorlevel%.
  +exit /b %errorlevel%
  +GOTO END
  +
  :NOQT
  @ECHO The QTDIR environment variable was NOT detected!
  