+revert:
+
+commit 1d3f61f8a799489f7f4d81e46d9e6b31a954ea4e
+Author: Louis Dionne <ldionne@apple.com>
+Date: Wed Apr 22 11:16:27 2020 -0400
+
+ [CMake] Enforce the minimum CMake version to be at least 3.13.4
+
+ This commit changes the warning for CMake < 3.13.4 into a fatal error.
+ The intent is to revert and re-apply this simple commit until all build
+ bots are migrated to CMake >= 3.13.4.
+
+ This is part of the effort discussed on llvm-dev here:
+
+ http://lists.llvm.org/pipermail/llvm-dev/2020-April/140578.html
+
+ Differential Revision: https://reviews.llvm.org/D78646
+
+--- a/llvm/CMakeLists.txt
++++ b/llvm/CMakeLists.txt
+@@ -3,9 +3,11 @@
+ cmake_minimum_required(VERSION 3.4.3)
+
+ if ("${CMAKE_VERSION}" VERSION_LESS "3.13.4")
+- message(FATAL_ERROR
+- "Your CMake version is ${CMAKE_VERSION}. The minimum version of CMake "
+- "required to build LLVM is now 3.13.4.")
++ message(WARNING
++ "Your CMake version is ${CMAKE_VERSION}. Starting with LLVM 12.0.0, the "
++ "minimum version of CMake required to build LLVM will become 3.13.4, and "
++ "using an older CMake will become an error. Please upgrade your CMake to "
++ "at least 3.13.4 now to avoid issues in the future!")
+ endif()
+
+ if(POLICY CMP0068)