[compiler-rt] Fix error in cmake. Check for empty list.

[mpividori]

Summary

Hi,
This patch fix an error in cmake:

CMake Error at projects/compiler-rt/cmake/config-ix.cmake:420 (list):
 list sub-command REMOVE_DUPLICATES requires list to be present.

Thanks

[mpividori]

@zturner I got that error again starting from scratch in a windows machine. So, I think we should add this patch.

[zturner]

Nit: Shouldn't the endif go after the message line though?

[mpividori]

@zturner Yes, you are right.

[mpividori]

@zturner, mmm in fact I think this is better. We can show the message if the list is empty.

cmake/config-ix.cmake

else()
     set(CAN_SYMBOLIZE 0)
   endif()
 else()
   set(CAN_SYMBOLIZE 1)
 endif()
 
 find_program(GOLD_EXECUTABLE NAMES ${LLVM_DEFAULT_TARGET_TRIPLE}-ld.gold ld.gold ${LLVM_DEFAULT_TARGET_TRIPLE}-ld ld DOC "The gold linker")
 
+if(COMPILER_RT_SUPPORTED_ARCH)
   list(REMOVE_DUPLICATES COMPILER_RT_SUPPORTED_ARCH)
+endif()
 message(STATUS "Compiler-RT supported architectures: ${COMPILER_RT_SUPPORTED_ARCH}")
 
 if(ANDROID)
   set(OS_NAME "Android")
 else()
   set(OS_NAME "${CMAKE_SYSTEM_NAME}")
 endif()