[compiler-rt] [compiler-rt] Use installed libc++(abi) for tests instead of build tree (PR #115077)

[Vincent Lee via llvm-commits]

================
@@ -680,15 +680,16 @@ macro(add_custom_libcxx name prefix)
 
   ExternalProject_Add(${name}
     DEPENDS ${name}-clobber ${LIBCXX_DEPS}
-    PREFIX ${CMAKE_CURRENT_BINARY_DIR}/${name}
+    PREFIX ${prefix}
     SOURCE_DIR ${LLVM_MAIN_SRC_DIR}/../runtimes
-    BINARY_DIR ${prefix}
+    BINARY_DIR ${prefix}/build
----------------
thevinster wrote:

Yes I saw that. In our case, the headers were defined under `${LIBCXX_${arch}_PREFIX}/build/include/c++/v1`, hence my suspicion on `/build` whether that was intentional But perhaps, it might a configuration issue on our end. For now, I've disabled building fuzzer since it's not needed for our internal workloads. 

https://github.com/llvm/llvm-project/pull/115077