Remove existing code

Author: jakeegan

compiler-rt/cmake/base-config-ix.cmake

@@ -14,11 +14,7 @@ include(CompilerRTDarwinUtils)
 check_include_file(unwind.h HAVE_UNWIND_H)
 
 # Used by sanitizer_common and tests.
-if (${CMAKE_SYSTEM_NAME} MATCHES AIX)
-  check_include_file(tirpc/rpc/xdr.h HAVE_RPC_XDR_H)
-else()
-  check_include_file(rpc/xdr.h HAVE_RPC_XDR_H)
-endif()
+check_include_file(rpc/xdr.h HAVE_RPC_XDR_H)
 if (NOT HAVE_RPC_XDR_H)
   set(HAVE_RPC_XDR_H 0)
 endif()