[llvm] cmake: do not force building with the install name dir (PR #65656)

[Raul Tambre via llvm-commits]

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@@ -6,7 +6,12 @@ set(LLVM_COMMON_CMAKE_UTILS ${CMAKE_CURRENT_SOURCE_DIR}/../cmake)
 include(${LLVM_COMMON_CMAKE_UTILS}/Modules/CMakePolicy.cmake
   NO_POLICY_SCOPE)
 
-set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
+# Builds with custom install names and installation rpath setups may not work
+# in the build tree. Allow these cases to use CMake's default build tree
+# behavior by setting `LLVM_USE_INSTALL_NAME_DIR_IN_BUILD_TREE` to do this.
+if (NOT LLVM_USE_INSTALL_NAME_DIR_IN_BUILD_TREE)
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tambry wrote:

The logic reads inverted to me. It seems `LLVM_USE_INSTALL_NAME_DIR_IN_BUILD_TREE=ON` should mean `CMAKE_BUILD_WITH_INSTALL_NAME_DIR=ON`, not the opposite.

https://github.com/llvm/llvm-project/pull/65656