set rpath for prepare_builtins build utility to find correct stage2
libs at runtime when executed as part of a build
Index: llvm-toolchain-12_12.0.1/libclc/CMakeLists.txt
===================================================================
--- llvm-toolchain-12_12.0.1.orig/libclc/CMakeLists.txt
+++ llvm-toolchain-12_12.0.1/libclc/CMakeLists.txt
@@ -139,6 +139,9 @@ target_compile_options( prepare_builtins
 target_compile_definitions( prepare_builtins PRIVATE ${LLVM_VERSION_DEFINE} )
 target_link_libraries( prepare_builtins PRIVATE ${LLVM_LIBS} )
 target_link_libraries( prepare_builtins PRIVATE ${LLVM_SYSTEM_LIBS} )
+set_target_properties( prepare_builtins
+                       PROPERTIES INSTALL_RPATH "${LLVM_LIBDIR}"
+                       BUILD_WITH_INSTALL_RPATH "ON")
 
 # Setup arch devices
 set( r600--_devices cedar cypress barts cayman )