[clang] [clang] fix clang_cmake_builddir (PR #155844)

[Romaric Jodin via cfe-commits]

https://github.com/rjodinchr updated https://github.com/llvm/llvm-project/pull/155844

>From bc8040d83f8ec6e89e4ff7476fa1745b32ea6d22 Mon Sep 17 00:00:00 2001
From: Romaric Jodin <rjodin at google.com>
Date: Thu, 28 Aug 2025 16:22:17 +0200
Subject: [PATCH 1/2] [clang] fix clang_cmake_builddir

When building llvm from a subdirectory (like clspv does)
`CMAKE_BINARY_DIR` is at the top of the build directory.

When building runtimes (libclc for example), the build fails looking
for clang (through `find_package` looking at `LLVM_BINARY_DIR` with
`NO_DEFAULT_PATH` & `NO_CMAKE_FIND_ROOT_PATH`) because clang is not in
`LLVM_BINARY_DIR`.

Fix that issue by setting `clang_cmake_builddir` the same way we set
`llvm_cmake_builddir` from `LLVM_BINARY_DIR`.

For default llvm build (using llvm as the main cmake project), it
should not change anything.
---
 clang/cmake/modules/CMakeLists.txt | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/clang/cmake/modules/CMakeLists.txt b/clang/cmake/modules/CMakeLists.txt
index d2d68121371bf..b3b4a74f6d470 100644
--- a/clang/cmake/modules/CMakeLists.txt
+++ b/clang/cmake/modules/CMakeLists.txt
@@ -8,15 +8,14 @@ include(FindPrefixFromConfig)
 # the usual CMake convention seems to be ${Project}Targets.cmake.
 set(CLANG_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/clang" CACHE STRING
   "Path for CMake subdirectory for Clang (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/clang')")
-# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
-set(clang_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
 
 # Keep this in sync with llvm/cmake/CMakeLists.txt!
 set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
   "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
 # CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
-string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_cmake_builddir "${LLVM_LIBRARY_DIR}")
-set(llvm_cmake_builddir "${llvm_cmake_builddir}/cmake/llvm")
+string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_builddir "${LLVM_LIBRARY_DIR}")
+set( llvm_cmake_builddir "${llvm_builddir}/cmake/llvm")
+set(clang_cmake_builddir "${llvm_builddir}/cmake/clang")
 
 get_property(CLANG_EXPORTS GLOBAL PROPERTY CLANG_EXPORTS)
 export(TARGETS ${CLANG_EXPORTS} FILE ${clang_cmake_builddir}/ClangTargets.cmake)

>From 8d691818558386e304448d269e448e4275ebcdb2 Mon Sep 17 00:00:00 2001
From: Romaric Jodin <rjodin at google.com>
Date: Thu, 11 Sep 2025 17:41:16 +0200
Subject: [PATCH 2/2] remove extra whitespace

---
 clang/cmake/modules/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/cmake/modules/CMakeLists.txt b/clang/cmake/modules/CMakeLists.txt
index b3b4a74f6d470..90fbd88ca9826 100644
--- a/clang/cmake/modules/CMakeLists.txt
+++ b/clang/cmake/modules/CMakeLists.txt
@@ -14,7 +14,7 @@ set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
   "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
 # CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
 string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_builddir "${LLVM_LIBRARY_DIR}")
-set( llvm_cmake_builddir "${llvm_builddir}/cmake/llvm")
+set(llvm_cmake_builddir "${llvm_builddir}/cmake/llvm")
 set(clang_cmake_builddir "${llvm_builddir}/cmake/clang")
 
 get_property(CLANG_EXPORTS GLOBAL PROPERTY CLANG_EXPORTS)