Use a custom version of clang in Xcode
This is a copy of my answer on StackOverflow: How can I force Xcode to use custom compiler?.


  People say it is possible with custom toolchains. I didn't make a research on them because easier solution worked well for me:
  
  
    It is also possible to run frontend plugins directly by setting appropriate "build settings" of Xcode. (Several ways to do this, you can set them on the command line for instance: xcodebuild build FOO=bla.) Here are a few build settings that I found useful to inject C flags: 
    
    OTHER_CFLAGS, OTHER_CPLUSPLUSFLAGS or to replace the compiler(s) and linker(s): 
    
    CC, CPLUSPLUS, LD, LDPLUSPLUS, LIBTOOL 
    
    The same approach works to control the "analyze" action: CLANG_ANALYZER_EXEC, CLANG_ANALYZER_OTHER_FLAGS 
    
    Disclaimer: some of those build settings are undocumented (afaik). Use at your own risk.
  
  
  (Taken from [cfe-dev] Compile/refactor iOS Xcode projects)
  
  For me it was enough to define the following User-Defined Settings in Build Settings of Xcode projects:
  
  CC=my-c-compiler
  
  CXX=my-cxx-compiler
  
  LIBTOOL=my-linker-for-static-libraries