Index: cmake/Modules/AddCompilerRT.cmake
===================================================================
--- cmake/Modules/AddCompilerRT.cmake
+++ cmake/Modules/AddCompilerRT.cmake
@@ -19,7 +19,7 @@
       set(libname "${name}.${os}")
       set(libnames ${libnames} ${libname})
       set(extra_cflags_${libname} ${DARWIN_${os}_CFLAGS})
-      list_union(LIB_ARCHS_${libname} DARWIN_${os}_ARCHS LIB_ARCHS)
+      list_intersect(LIB_ARCHS_${libname} DARWIN_${os}_ARCHS LIB_ARCHS)
     endforeach()
   else()
     foreach(arch ${LIB_ARCHS})
@@ -87,7 +87,7 @@
         set(libname "${name}_${os}_dynamic")
         set(extra_linkflags_${libname} ${DARWIN_${os}_LINKFLAGS} ${LIB_LINKFLAGS})
       endif()
-      list_union(LIB_ARCHS_${libname} DARWIN_${os}_ARCHS LIB_ARCHS)
+      list_intersect(LIB_ARCHS_${libname} DARWIN_${os}_ARCHS LIB_ARCHS)
       if(LIB_ARCHS_${libname})
         list(APPEND libnames ${libname})
         set(extra_cflags_${libname} ${DARWIN_${os}_CFLAGS} ${LIB_CFLAGS})
Index: cmake/Modules/CompilerRTDarwinUtils.cmake
===================================================================
--- cmake/Modules/CompilerRTDarwinUtils.cmake
+++ cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -91,7 +91,7 @@
 # This function checks the host cpusubtype to see if it is post-haswell. Haswell
 # and later machines can run x86_64h binaries. Haswell is cpusubtype 8.
 function(darwin_filter_host_archs input output)
-  list_union(tmp_var DARWIN_osx_ARCHS ${input})
+  list_intersect(tmp_var DARWIN_osx_ARCHS ${input})
   execute_process(
     COMMAND sysctl hw.cpusubtype
     OUTPUT_VARIABLE SUBTYPE)
@@ -285,7 +285,7 @@
                       ../profile/InstrProfilingPlatformDarwin
                       ../profile/InstrProfilingWriter)
   foreach (os ${ARGN})
-    list_union(DARWIN_BUILTIN_ARCHS DARWIN_${os}_ARCHS BUILTIN_SUPPORTED_ARCH)
+    list_intersect(DARWIN_BUILTIN_ARCHS DARWIN_${os}_ARCHS BUILTIN_SUPPORTED_ARCH)
     foreach (arch ${DARWIN_BUILTIN_ARCHS})
       darwin_find_excluded_builtins_list(${arch}_${os}_EXCLUDED_BUILTINS
                               OS ${os}
Index: cmake/Modules/CompilerRTUtils.cmake
===================================================================
--- cmake/Modules/CompilerRTUtils.cmake
+++ cmake/Modules/CompilerRTUtils.cmake
@@ -58,7 +58,7 @@
   list(APPEND ${list} "${varname}=${${varname}}")
 endmacro()
 
-macro(list_union output input1 input2)
+macro(list_intersect output input1 input2)
   set(${output})
   foreach(it ${${input1}})
     list(FIND ${input2} ${it} index)
Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -488,42 +488,42 @@
     endforeach()
   endif()
 
-  # for list_union
+  # for list_intersect
   include(CompilerRTUtils)
 
-  list_union(BUILTIN_SUPPORTED_ARCH ALL_BUILTIN_SUPPORTED_ARCH toolchain_arches)
+  list_intersect(BUILTIN_SUPPORTED_ARCH ALL_BUILTIN_SUPPORTED_ARCH toolchain_arches)
 
-  list_union(SANITIZER_COMMON_SUPPORTED_ARCH
+  list_intersect(SANITIZER_COMMON_SUPPORTED_ARCH
     ALL_SANITIZER_COMMON_SUPPORTED_ARCH
     COMPILER_RT_SUPPORTED_ARCH
     )
   set(LSAN_COMMON_SUPPORTED_ARCH ${SANITIZER_COMMON_SUPPORTED_ARCH})
   set(UBSAN_COMMON_SUPPORTED_ARCH ${SANITIZER_COMMON_SUPPORTED_ARCH})
-  list_union(ASAN_SUPPORTED_ARCH
+  list_intersect(ASAN_SUPPORTED_ARCH
     ALL_ASAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(DFSAN_SUPPORTED_ARCH
+  list_intersect(DFSAN_SUPPORTED_ARCH
     ALL_DFSAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(LSAN_SUPPORTED_ARCH
+  list_intersect(LSAN_SUPPORTED_ARCH
     ALL_LSAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(MSAN_SUPPORTED_ARCH
+  list_intersect(MSAN_SUPPORTED_ARCH
     ALL_MSAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(PROFILE_SUPPORTED_ARCH
+  list_intersect(PROFILE_SUPPORTED_ARCH
     ALL_PROFILE_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(TSAN_SUPPORTED_ARCH
+  list_intersect(TSAN_SUPPORTED_ARCH
     ALL_TSAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(UBSAN_SUPPORTED_ARCH
+  list_intersect(UBSAN_SUPPORTED_ARCH
     ALL_UBSAN_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(SAFESTACK_SUPPORTED_ARCH
+  list_intersect(SAFESTACK_SUPPORTED_ARCH
     ALL_SAFESTACK_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
-  list_union(CFI_SUPPORTED_ARCH
+  list_intersect(CFI_SUPPORTED_ARCH
     ALL_CFI_SUPPORTED_ARCH
     SANITIZER_COMMON_SUPPORTED_ARCH)
 else()