diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
--- a/compiler-rt/cmake/config-ix.cmake
+++ b/compiler-rt/cmake/config-ix.cmake
@@ -250,7 +250,31 @@
   endif()
   set(test_cflags "")
   get_target_flags_for_arch(${arch} test_cflags)
-  list(APPEND test_cflags ${DARWIN_${platform}_CFLAGS})
+
+  if (NOT "${arch}" STREQUAL "arm64e")
+    list(APPEND test_cflags ${DARWIN_${platform}_CFLAGS})
+  else()
+    # arm64e is not currently ABI stable so we need to build for the
+    # OS version being tested. Rather than querying the device under test
+    # we use the SDK version which "should" be the same as the
+    # device under test (it is a configuration error for these not to match).
+    # FIXME(dliew): We can remove this if we build the runtimes with the appropriate
+    # deployment target for arm64e.
+    foreach (flag ${DARWIN_${platform}_CFLAGS})
+      if ("${flag}" MATCHES "^${DARWIN_${platform}_MIN_VER_FLAG}=.+")
+        # Find the SDK version
+        get_xcrun_platform_from_apple_platform("${platform}" xcrun_platform_name)
+        find_darwin_sdk_version(platform_sdk_version "${xcrun_platform_name}")
+        # Patch flag with correct deployment target
+        set(replacement_flag "${DARWIN_${platform}_MIN_VER_FLAG}=${platform_sdk_version}")
+        list(APPEND test_cflags "${replacement_flag}")
+      else()
+        # Copy through
+        list(APPEND test_cflags "${flag}")
+      endif()
+    endforeach()
+  endif()
+
   string(REPLACE ";" " " test_cflags_str "${test_cflags}")
   string(APPEND test_cflags_str "${COMPILER_RT_TEST_COMPILER_CFLAGS}")
   set(${cflags_out} "${test_cflags_str}" PARENT_SCOPE)
@@ -279,6 +303,30 @@
   set(${is_valid_out} ${is_valid} PARENT_SCOPE)
 endfunction()
 
+# Maps the Apple platform name used in Compiler-rt's CMake code
+# to the name recognised by xcrun's `--sdk` argument
+function(get_xcrun_platform_from_apple_platform platform out_var)
+  set(xcrun_platform "")
+  if ("${platform}" STREQUAL "osx")
+    set(xcrun_platform "macosx")
+  elseif ("${platform}" STREQUAL "iossim")
+    set(xcrun_platform "iphonesimulator")
+  elseif ("${platform}" STREQUAL "ios")
+    set(xcrun_platform "iphoneos")
+  elseif ("${platform}" STREQUAL "watchossim")
+    set(xcrun_platform "watchsimulator")
+  elseif ("${platform}" STREQUAL "watchos")
+    set(xcrun_platform "watchos")
+  elseif ("${platform}" STREQUAL "tvossim")
+    set(xcrun_platform "appletvsimulator")
+  elseif ("${platform}" STREQUAL "tvos")
+    set(xcrun_platform "appletvos")
+  else()
+    message(FATAL_ERROR "\"${platform}\" is not a handled apple platform")
+  endif()
+  set(${out_var} ${xcrun_platform} PARENT_SCOPE)
+endfunction()
+
 include(AllSupportedArchDefs)
 
 if(APPLE)