Fix non-PIC build after 253959

CMAKE_EXE_LINKER_FLAGS is a string. Appending a flag using list(APPEND) introduces an extra
semicolon which breaks stuff. Change this to append the value in the same way that everyone else
seems to be doing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253968 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/config-ix.cmake

@@ -301,7 +301,7 @@ else()
   set(ENABLE_PIC 0)
   check_cxx_compiler_flag("-fno-pie" SUPPORTS_NO_PIE_FLAG)
   if(SUPPORTS_NO_PIE_FLAG)
-    list(APPEND CMAKE_EXE_LINKER_FLAGS "-fno-pie")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fno-pie")
   endif()
 endif()