[CMake] Pass through CMAKE_READELF to subbuilds

This matches handling of other CMake variables.

Differential Revision: https://reviews.llvm.org/D110463

clang/CMakeLists.txt

@@ -759,6 +759,7 @@ if (CLANG_ENABLE_BOOTSTRAP)
       add_dependencies(clang-bootstrap-deps llvm-objcopy llvm-strip)
       set(${CLANG_STAGE}_OBJCOPY -DCMAKE_OBJCOPY=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-objcopy)
       set(${CLANG_STAGE}_STRIP -DCMAKE_STRIP=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-strip)
+      set(${CLANG_STAGE}_READELF -DCMAKE_READELF=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-readelf)
     endif()
   endif()
 

compiler-rt/cmake/Modules/AddCompilerRT.cmake

@@ -598,6 +598,7 @@ macro(add_custom_libcxx name prefix)
     CMAKE_OBJCOPY
     CMAKE_OBJDUMP
     CMAKE_STRIP
+    CMAKE_READELF
     CMAKE_SYSROOT
     LIBCXX_HAS_MUSL_LIBC
     PYTHON_EXECUTABLE

llvm/cmake/modules/LLVMExternalProjectUtils.cmake

@@ -244,7 +244,8 @@ function(llvm_ExternalProject_Add name source_dir)
                       -DCMAKE_NM=${CMAKE_NM}
                       -DCMAKE_OBJCOPY=${CMAKE_OBJCOPY}
                       -DCMAKE_OBJDUMP=${CMAKE_OBJDUMP}
-                      -DCMAKE_STRIP=${CMAKE_STRIP})
+                      -DCMAKE_STRIP=${CMAKE_STRIP}
+                      -DCMAKE_READELF=${CMAKE_READELF})
     set(llvm_config_path ${LLVM_CONFIG_PATH})
 
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")