build: bump to CMake 3.16, centralise artifacts

Put all the libraries into lib, all the binaries into bin.  This bumps
up the CMake requirement to 3.16.0 to enable the co-located artifacts.
It should make it easier for people to find the artifacts in the build
tree.

Author: compnerd

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15.1)
+cmake_minimum_required(VERSION 3.16.0)
 project(TensorFlow
   LANGUAGES Swift)
 
@@ -18,6 +18,9 @@ endif()
 
 list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/modules)
 
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
 option(USE_BUNDLED_X10