[llvm] [openmp] Deprecate LLVM_ENABLE_PROJECTS in favor of LLVM_ENABLE_RUNTIMES (PR #124711)

[Petr Hosek via llvm-commits]

https://github.com/petrhosek created https://github.com/llvm/llvm-project/pull/124711

We plan to make this a hard error in the LLVM 21 release.

Link #124014

>From af7a1058b6415e14818043ba723b17b5d6a0c627 Mon Sep 17 00:00:00 2001
From: Petr Hosek <phosek at google.com>
Date: Tue, 28 Jan 2025 07:05:09 +0000
Subject: [PATCH] [openmp] Deprecate LLVM_ENABLE_PROJECTS in favor of
 LLVM_ENABLE_RUNTIMES

We plan to make this a hard error in the LLVM 21 release.

Link #124014
---
 llvm/CMakeLists.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index c9ff3696e22d69..4cb4e90fa5c7e8 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -164,6 +164,13 @@ if ("compiler-rt" IN_LIST LLVM_ENABLE_PROJECTS)
     "https://compiler-rt.llvm.org/ for building the runtimes.")
 endif()
 
+if ("openmp" IN_LIST LLVM_ENABLE_PROJECTS)
+  message(WARNING "Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will "
+    "become a fatal error in the LLVM 21 release.  Please use "
+    "-DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at "
+    "https://openmp.llvm.org/ for building the runtimes.")
+endif()
+
 # Select the runtimes to build
 #
 # As we migrate runtimes to using the bootstrapping build, the set of default runtimes