Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -205,6 +205,32 @@
   endif()
 endmacro()
 
+# Returns CFLAGS that should be used to run tests for the
+# specific apple platform and architecture.
+function(get_test_cflags_for_apple_platform platform arch cflags_out)
+  is_valid_apple_platform("${platform}" is_valid_platform)
+  if (NOT is_valid_platform)
+    message(FATAL_ERROR "\"${platform}\" is not a valid apple platform")
+  endif()
+  set(test_cflags "")
+  get_target_flags_for_arch(${arch} test_cflags)
+  list(APPEND test_cflags ${DARWIN_${platform}_CFLAGS})
+  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)
+endfunction()
+
+function(is_valid_apple_platform platform is_valid_out)
+  set(is_valid FALSE)
+  if ("${platform}" STREQUAL "")
+    message(FATAL_ERROR "platform cannot be empty")
+  endif()
+  if ("${platform}" MATCHES "^(osx|((ios|watchos|tvos)(sim)?))$")
+    set(is_valid TRUE)
+  endif()
+  set(${is_valid_out} ${is_valid} PARENT_SCOPE)
+endfunction()
+
 set(ARM64 aarch64)
 set(ARM32 arm armhf)
 set(HEXAGON hexagon)
Index: test/asan/CMakeLists.txt
===================================================================
--- test/asan/CMakeLists.txt
+++ test/asan/CMakeLists.txt
@@ -89,7 +89,11 @@
   foreach(arch ${DARWIN_iossim_ARCHS})
     set(ASAN_TEST_APPLE_PLATFORM "iossim")
     set(ASAN_TEST_TARGET_ARCH ${arch})
-    set(ASAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_iossim_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
+    get_test_cflags_for_apple_platform(
+      "${ASAN_TEST_APPLE_PLATFORM}"
+      "${ASAN_TEST_TARGET_ARCH}"
+      ASAN_TEST_TARGET_CFLAGS
+      )
     set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-${ASAN_TEST_APPLE_PLATFORM}")
     get_bits_for_arch(${arch} ASAN_TEST_BITS)
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
@@ -106,7 +110,10 @@
   foreach (arch ${DARWIN_ios_ARCHS})
     set(ASAN_TEST_APPLE_PLATFORM "ios")
     set(ASAN_TEST_TARGET_ARCH ${arch})
-    set(ASAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
+    get_test_cflags_for_apple_platform(
+      "${ASAN_TEST_APPLE_PLATFORM}"
+      "${arch}"
+      ASAN_TEST_TARGET_CFLAGS)
     set(ASAN_TEST_CONFIG_SUFFIX "-${arch}-${ASAN_TEST_APPLE_PLATFORM}")
     get_bits_for_arch(${arch} ASAN_TEST_BITS)
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
Index: test/fuzzer/CMakeLists.txt
===================================================================
--- test/fuzzer/CMakeLists.txt
+++ test/fuzzer/CMakeLists.txt
@@ -91,7 +91,11 @@
   foreach(arch ${DARWIN_ios_ARCHS})
     set(LIBFUZZER_TEST_APPLE_PLATFORM "ios")
     set(LIBFUZZER_TEST_TARGET_ARCH ${arch})
-    set(LIBFUZZER_TEST_FLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
+    get_test_cflags_for_apple_platform(
+      "${LIBFUZZER_TEST_APPLE_PLATFORM}"
+      "${LIBFUZZER_TEST_TARGET_ARCH}"
+      LIBFUZZER_TEST_FLAGS
+      )
     set(LIBFUZZER_TEST_CONFIG_SUFFIX "-${arch}-${LIBFUZZER_TEST_APPLE_PLATFORM}")
     string(TOUPPER ${arch} ARCH_UPPER_CASE)
     set(CONFIG_NAME "IOS${ARCH_UPPER_CASE}Config")
Index: test/tsan/CMakeLists.txt
===================================================================
--- test/tsan/CMakeLists.txt
+++ test/tsan/CMakeLists.txt
@@ -56,7 +56,11 @@
   set(TSAN_TEST_APPLE_PLATFORM "iossim")
   set(arch "x86_64")
   set(TSAN_TEST_TARGET_ARCH ${arch})
-  set(TSAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_iossim_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
+  get_test_cflags_for_apple_platform(
+    "${TSAN_TEST_APPLE_PLATFORM}"
+    "${TSAN_TEST_TARGET_ARCH}"
+    TSAN_TEST_TARGET_CFLAGS
+    )
   set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-${TSAN_TEST_APPLE_PLATFORM}")
   string(TOUPPER ${arch} ARCH_UPPER_CASE)
   set(CONFIG_NAME "IOSSim${ARCH_UPPER_CASE}Config")
@@ -71,7 +75,11 @@
   set(TSAN_TEST_APPLE_PLATFORM "ios")
   set(arch "arm64")
   set(TSAN_TEST_TARGET_ARCH ${arch})
-  set(TSAN_TEST_TARGET_CFLAGS "-arch ${arch} -isysroot ${DARWIN_ios_SYSROOT} ${COMPILER_RT_TEST_COMPILER_CFLAGS}")
+  get_test_cflags_for_apple_platform(
+    "${TSAN_TEST_APPLE_PLATFORM}"
+    "${TSAN_TEST_TARGET_ARCH}"
+    TSAN_TEST_TARGET_CFLAGS
+    )
   set(TSAN_TEST_CONFIG_SUFFIX "-${arch}-${TSAN_TEST_APPLE_PLATFORM}")
   string(TOUPPER ${arch} ARCH_UPPER_CASE)
   set(CONFIG_NAME "IOS${ARCH_UPPER_CASE}Config")
Index: test/ubsan/CMakeLists.txt
===================================================================
--- test/ubsan/CMakeLists.txt
+++ test/ubsan/CMakeLists.txt
@@ -113,10 +113,11 @@
   endif()
   foreach(platform ${UBSAN_APPLE_PLATFORMS})
     foreach(arch ${DARWIN_${platform}_ARCHS})
-      get_target_flags_for_arch(${arch} UBSAN_TEST_TARGET_ARCH_FLAGS_AS_LIST)
-      string(REPLACE ";" " " UBSAN_TEST_TARGET_ARCH_FLAGS "${UBSAN_TEST_TARGET_ARCH_FLAGS_AS_LIST}")
-      set(UBSAN_TEST_TARGET_CFLAGS
-        "${UBSAN_TEST_TARGET_ARCH_FLAGS} -isysroot ${DARWIN_${platform}_SYSROOT}")
+      get_test_cflags_for_apple_platform(
+        "${platform}"
+        "${arch}"
+        UBSAN_TEST_TARGET_CFLAGS
+      )
       if (";${UBSAN_SUPPORTED_ARCH};" MATCHES ";${arch};")
         add_ubsan_device_testsuite("Standalone" ubsan ${platform} ${arch})
       endif()