I\'ve just upgraded to Xcode 5 beta with the April 15 2013 commandline tools and hit the following warning when running a cmake build during the standard CMakeTestCCompiler.
run this comment on your client.app:
export PATH=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:$PATH
The problem was that Xcode 5 replaces gcc with clang and adds in a "-triple" option that specifies OSX as the target. If you pass "-miphoneos-version-min=7.0" on both gcc command lines it works. You can see the clang command line if you pass "--verbose" to gcc. It's also necessary to add to the PATH for Xcode 5 so that cmake can find the necessary tools: export PATH=/Applications/Xcode5-DP6.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin:/Applications/Xcode5-DP6.app/Contents/Developer/usr/bin:$PATH None of this is official.. but works for me so far.