[CMake] Add more runtime configurations.

Summary:
- `project` is required when `runtime/CMakeList.txt` is the top-level `CMakeList.txt` file. This will establish version and policy settings.

- `-D_FILE_OFFSET_BITS=64` should never be set for Android runtimes.

Reviewers: srhines, pirama, beanz

Subscribers: llvm-commits, srhines, mgorny

Differential Revision: https://reviews.llvm.org/D35648

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312302 91177308-0d34-0410-b5e6-96231b3b80d8

runtimes/CMakeLists.txt

@@ -24,6 +24,7 @@ if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
   endfunction()
 
   cmake_minimum_required(VERSION 3.4.3)
+  project(Runtimes C CXX ASM)
 
   # Add the root project's CMake modules, and the LLVM build's modules to the
   # CMake module path.