[libc] Remove a now uneccesary CMake policy.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.org/D143139

Author: Siva Chandra Reddy

libc/CMakeLists.txt

@@ -3,9 +3,6 @@ cmake_minimum_required(VERSION 3.13.4)
 # Default to C++17
 set(CMAKE_CXX_STANDARD 17)
 
-# Use old version of target_sources command which converts the source
-# file paths to full paths.
-cmake_policy(SET CMP0076 OLD)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 # The top-level sourse and binary directories.