Raising minimum required CMake version to 2.8.12.2.

[beanz]

Summary

Based on the discussion on LLVMDev, LLVM is going to raise the minimum required CMake version to 2.8.12.2. These are the cooresponding changes to clang. It is not required for clang to move in lock step with LLVM, but it does simplify things.

LLVMDev thread: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-February/081966.html

[chandlerc]

Unsure if you were actually looking for review of this Chris, but it looks fine.

[beanz]

I was mostly providing this for the benefit of the thread. I've landed some very similar patches, and we're now at 2.8.12.2!

CMakeLists.txt

 cmake_minimum_required(VERSION 2.8.8)
 
-# FIXME: It may be removed when we use 2.8.12.
-if(CMAKE_VERSION VERSION_LESS 2.8.12)
-  # Invalidate a couple of keywords.
-  set(cmake_2_8_12_INTERFACE)
-  set(cmake_2_8_12_PRIVATE)
-else()
-  # Use ${cmake_2_8_12_KEYWORD} intead of KEYWORD in target_link_libraries().
-  set(cmake_2_8_12_INTERFACE INTERFACE)
-  set(cmake_2_8_12_PRIVATE PRIVATE)
-  if(POLICY CMP0022)
-    cmake_policy(SET CMP0022 NEW) # automatic when 2.8.12 is required
-  endif()
-endif()
 
 # If we are not building as a part of LLVM, build Clang as an
 # standalone project, using LLVM as an external library:
 if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
   project(Clang)
 
   # Rely on llvm-config.
   set(CONFIG_OUTPUT)
set(srcs
       ADDITIONAL_HEADERS
       ${srcs}
       ${ARG_ADDITIONAL_HEADERS} # It may contain unparsed unknown args.
       )
   endif()
   llvm_add_library(${name} ${ARG_UNPARSED_ARGUMENTS} ${srcs})
 
   if(TARGET ${name})
-    target_link_libraries(${name} ${cmake_2_8_12_INTERFACE} ${LLVM_COMMON_LIBS})
+    target_link_libraries(${name} INTERFACE ${LLVM_COMMON_LIBS})
 
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "libclang")
       install(TARGETS ${name}
         LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
         ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
         RUNTIME DESTINATION bin)
     endif()
     set_property(GLOBAL APPEND PROPERTY CLANG_EXPORTS ${name})

examples/PrintFunctionNames/CMakeLists.txt

 # If we don't need RTTI or EH, there's no reason to export anything
 # from the plugin.
 if( NOT MSVC ) # MSVC mangles symbols differently, and
                 # PrintFunctionNames.export contains C++ symbols.
   if( NOT LLVM_REQUIRES_RTTI )
     if( NOT LLVM_REQUIRES_EH )
       set(LLVM_EXPORTED_SYMBOL_FILE ${CMAKE_CURRENT_SOURCE_DIR}/PrintFunctionNames.exports)
     endif()
   endif()
 endif()
 
 add_llvm_loadable_module(PrintFunctionNames PrintFunctionNames.cpp)
 
 if(LLVM_ENABLE_PLUGINS AND (WIN32 OR CYGWIN))
-  target_link_libraries(PrintFunctionNames ${cmake_2_8_12_PRIVATE}
+  target_link_libraries(PrintFunctionNames PRIVATE
     clangAST
     clangBasic
     clangFrontend
     LLVMSupport
     )
 endif()

examples/analyzer-plugin/CMakeLists.txt

 add_llvm_loadable_module(SampleAnalyzerPlugin MainCallChecker.cpp)
 
 if(LLVM_ENABLE_PLUGINS AND (WIN32 OR CYGWIN))
-  target_link_libraries(SampleAnalyzerPlugin ${cmake_2_8_12_PRIVATE}
+  target_link_libraries(SampleAnalyzerPlugin PRIVATE
     clangAnalysis
     clangAST
     clangStaticAnalyzerCore
     LLVMSupport
     )
 endif()