File compiler-rt-fix-relative-path.patch of Package llvm21

diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 1dadb6a810ef..956ff3d1b006 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -64,7 +64,7 @@ include(CMakePushCheckState)
 option(COMPILER_RT_BUILTINS_HIDE_SYMBOLS
   "Do not export any symbols from the static library." ON)
 
-include_directories(../../../third-party/siphash/include)
+include_directories(${CMAKE_SOURCE_DIR}/../third-party/siphash/include)
 
 # TODO: Need to add a mechanism for logging errors when builtin source files are
 # added to a sub-directory and not this CMakeLists file.