[cmake] Remove policy conditionals

[smeenai]

Summary

LLVM now requires a minimum of cmake 3.4.3, and all the policies
currently being set are present in that cmake version, so the
conditionals will always be true and are therefore unnecessary. The
movation is that the conditionals can give the false impression that the
policy settings are optional, whereas for example it's necessary to set
CMP0056 in order for check_linker_flags to operate correctly after
r316972. Inline the project version and language setting in the process.

CMakeLists.txt

 # See docs/CMake.html for instructions about how to build LLVM with CMake.
 
 cmake_minimum_required(VERSION 3.4.3)
 
-if(POLICY CMP0022)
-  cmake_policy(SET CMP0022 NEW) # automatic when 2.8.12 is required
-endif()
+cmake_policy(SET CMP0022 NEW)
+
+cmake_policy(SET CMP0048 NEW)
 
-if (POLICY CMP0051)
-  # CMake 3.1 and higher include generator expressions of the form
-  # $<TARGETLIB:obj> in the SOURCES property.  These need to be
-  # stripped everywhere that access the SOURCES property, so we just
-  # defer to the OLD behavior of not including generator expressions
-  # in the output for now.
-  cmake_policy(SET CMP0051 OLD)
-endif()
 
-if(POLICY CMP0056)
-  cmake_policy(SET CMP0056 NEW)
-endif()
 
-if(POLICY CMP0057)
-  cmake_policy(SET CMP0057 NEW)
-endif()
 
 if(NOT DEFINED LLVM_VERSION_MAJOR)
   set(LLVM_VERSION_MAJOR 6)
 endif()
 if(NOT DEFINED LLVM_VERSION_MINOR)
   set(LLVM_VERSION_MINOR 0)
 endif()
 if(NOT DEFINED LLVM_VERSION_PATCH)
   set(LLVM_VERSION_PATCH 0)
 endif()
 if(NOT DEFINED LLVM_VERSION_SUFFIX)
   set(LLVM_VERSION_SUFFIX svn)
 endif()
 
-if (POLICY CMP0048)
-  cmake_policy(SET CMP0048 NEW)
-  set(cmake_3_0_PROJ_VERSION
-    VERSION ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH})
-  set(cmake_3_0_LANGUAGES LANGUAGES)
-endif()
-
 if (NOT PACKAGE_VERSION)
   set(PACKAGE_VERSION
     "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}${LLVM_VERSION_SUFFIX}")
 endif()
 
 if ((CMAKE_GENERATOR MATCHES "Visual Studio") AND (CMAKE_GENERATOR_TOOLSET STREQUAL ""))
   message(WARNING "Visual Studio generators use the x86 host compiler by "
                   "default, even for 64-bit targets. This can result in linker "
                   "instability and out of memory errors. To use the 64-bit "
                   "host compiler, pass -Thost=x64 on the CMake command line.")
 endif()
 
 project(LLVM
-  ${cmake_3_0_PROJ_VERSION}
-  ${cmake_3_0_LANGUAGES}
-  C CXX ASM)
+  VERSION ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}
+  LANGUAGES C CXX ASM)
 
 if (NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
   message(STATUS "No build type selected, default to Debug")
   set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Build type (default Debug)" FORCE)
 endif()
 
 # This should only apply if you are both on an Apple host, and targeting Apple.
 if(CMAKE_HOST_APPLE AND APPLE)