From cade66d842a894075938bc5528475d9fcd8bd559 Mon Sep 17 00:00:00 2001
From: Chris Marsh <chrismarsh.c2@gmail.com>
Date: Thu, 29 Aug 2024 12:49:53 -0600
Subject: [PATCH] CMakePackage: Set policy CMP0042 NEW on macos (#46114)

so linking to shared libraries works well at runtime on darwin for all packages with cmake_minimum_required < 3.
---
 lib/spack/spack/build_systems/cmake.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/spack/spack/build_systems/cmake.py b/lib/spack/spack/build_systems/cmake.py
index a64904715e0..10949e79498 100644
--- a/lib/spack/spack/build_systems/cmake.py
+++ b/lib/spack/spack/build_systems/cmake.py
@@ -108,6 +108,11 @@ def _conditional_cmake_defaults(pkg: spack.package_base.PackageBase, args: List[
     if _supports_compilation_databases(pkg):
         args.append(CMakeBuilder.define("CMAKE_EXPORT_COMPILE_COMMANDS", True))
 
+    # Enable MACOSX_RPATH by default when cmake_minimum_required < 3
+    # https://cmake.org/cmake/help/latest/policy/CMP0042.html
+    if pkg.spec.satisfies("platform=darwin") and cmake.satisfies("@3:"):
+        args.append(CMakeBuilder.define("CMAKE_POLICY_DEFAULT_CMP0042", "NEW"))
+
 
 def generator(*names: str, default: Optional[str] = None):
     """The build system generator to use.