[CMake] Remove dead code setting policies to NEW

cmake_minimum_required(VERSION) calls cmake_policy(VERSION),
which sets all policies up to VERSION to NEW.
LLVM started requiring CMake 3.13 last year, so we can remove
a bunch of code setting policies prior to 3.13 to NEW as it
no longer has any effect.

Reviewed By: phosek, #libunwind, #libc, #libc_abi, ldionne

Differential Revision: https://reviews.llvm.org/D94374

GitOrigin-RevId: 480643a95cd157e654f4f97e8231b18850e7d79a
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e344263..8ae32fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,10 +8,6 @@
 cmake_minimum_required(VERSION 3.13.4)
-if (POLICY CMP0042)
-  cmake_policy(SET CMP0042 NEW) # Set MACOSX_RPATH=YES by default
 # Add path for custom modules