title: spacing in -D option in cmake
body: <p><code>-D CMAKE_C_COMPILER</code> is what I use to choose my compiler. However, if I have CMake options that are turned on/off like <code>USEIPHONEFLAG</code>, I need to do <code>-DUSEIPHONEFLAG=1</code>, <code>-D USEIPHONEFLAG=1</code> does not work. I was wondering how the space after <code>-D</code> works in CMake.</p>