Remove cmake legacy code

[labath]

Summary

Cmake 2.8 support is gone and not coming back. We can remove a bit of legacy code now.

cmake/modules/AddLLDB.cmake

 function(lldb_link_common_libs name targetkind)
   if (NOT LLDB_USED_LIBS)
     return()
   endif()
 
   if(${targetkind} MATCHES "SHARED")
-    set(LINK_KEYWORD ${cmake_2_8_12_PUBLIC})
+    set(LINK_KEYWORD PUBLIC)
   endif()
 
   if(${targetkind} MATCHES "SHARED" OR ${targetkind} MATCHES "EXE")
     if (LLDB_LINKER_SUPPORTS_GROUPS)
       target_link_libraries(${name} ${LINK_KEYWORD}
                             -Wl,--start-group ${LLDB_USED_LIBS} -Wl,--end-group)
     else()
       target_link_libraries(${name} ${LINK_KEYWORD} ${LLDB_USED_LIBS})
if (PARAM_OBJECT)
     add_library(${name} ${libkind} ${srcs})
   else()
     llvm_add_library(${name} ${libkind} DISABLE_LLVM_LINK_LLVM_DYLIB ${srcs})
 
     lldb_link_common_libs(${name} "${libkind}")
 
     if (PARAM_SHARED)
       if (LLDB_LINKER_SUPPORTS_GROUPS)
-        target_link_libraries(${name} ${cmake_2_8_12_PUBLIC}
+        target_link_libraries(${name} PUBLIC
                     -Wl,--start-group ${CLANG_USED_LIBS} -Wl,--end-group)
       else()
-        target_link_libraries(${name} ${cmake_2_8_12_PUBLIC} ${CLANG_USED_LIBS})
+        target_link_libraries(${name} PUBLIC ${CLANG_USED_LIBS})
       endif()
     endif()
     llvm_config(${name} ${LLVM_LINK_COMPONENTS} ${LLVM_PRIVATE_LINK_COMPONENTS})
 
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "liblldb")
       if (PARAM_SHARED)
         install(TARGETS ${name}
           RUNTIME DESTINATION bin

cmake/modules/LLDBConfig.cmake

 "`CMakeFiles'. Please delete them.")
 endif()
 
 # Compute the LLDB version from the LLVM version.
 string(REGEX MATCH "[0-9]+\\.[0-9]+(\\.[0-9]+)?" LLDB_VERSION
   ${PACKAGE_VERSION})
 message(STATUS "LLDB version: ${LLDB_VERSION}")
 
-if (CMAKE_VERSION VERSION_LESS 2.8.12)
-  set(cmake_2_8_12_INTERFACE)
-  set(cmake_2_8_12_PRIVATE)
-  set(cmake_2_8_12_PUBLIC)
-else ()
-  set(cmake_2_8_12_INTERFACE INTERFACE)
-  set(cmake_2_8_12_PRIVATE PRIVATE)
-  set(cmake_2_8_12_PUBLIC PUBLIC)
-endif ()
-
 include_directories(BEFORE
   ${CMAKE_CURRENT_BINARY_DIR}/include
   ${CMAKE_CURRENT_SOURCE_DIR}/include
   )
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/
     DESTINATION include

source/API/CMakeLists.txt

set_target_properties(liblldb
     PROPERTIES
     OUTPUT_NAME lldb
     )
 endif()
 
 if (LLDB_WRAP_PYTHON)
   add_dependencies(liblldb swig_wrapper)
 endif()
-target_link_libraries(liblldb ${cmake_2_8_12_PRIVATE} ${LLDB_SYSTEM_LIBS})
+target_link_libraries(liblldb PRIVATE ${LLDB_SYSTEM_LIBS})