title: Pass parameter with spaces to CMake ExternalProject_Add BUILD_COMMAND
body: <p>I'm trying to cross compile bzip2 in Linux utilizing CMake's <code>ExternalProject_Add(...)</code> command.</p>
  
  <p>However, in order to cross-compile libbzip, you must modify some of the Makefile macros to execute the build. Here is my current cross compile variable:</p>
  
  <pre><code>set(bzlib_CROSS CC=${CROSS_PREFIX}gcc AR=${CROSS_PREFIX}ar RANLIB=${CROSS_PREFIX}ranlib LDFLAGS=-L${bzlib_MINGW_SRC}/lib CFLAGS=-Wall -Winline -O2 -g -I${bzlib_MINGW_SRC}/include)
  </code></pre>
  
  <p>This variable is then used for the build command</p>
  
  <pre><code>set(bzlib_BUILD make ${bzlib_CROSS} PREFIX=${DEPENDENCY_DIR})
  </code></pre>
  
  <p>CMake errors because it is trying to pass -O2, -g, etc. to <code>make</code>, which of course doesn't work, but when I try to add quotes around the <code>CFLAGS</code> variable it says</p>
  
  <pre><code>cc1: error: unrecognized command line option '-Wall -Winline -O2 -g -I/long/path/here/include'
  </code></pre>
  
  <p>Is it possible to set a Makefile macro with spaces in it using CMake's <code>BUILD_COMMAND</code>? Thanks!</p>