Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -295,6 +295,9 @@
   string(REGEX MATCH "-mmacosx-version-min="
          MACOSX_VERSION_MIN_FLAG "${CMAKE_CXX_FLAGS}")
   set(SANITIZER_COMMON_SUPPORTED_DARWIN_OS osx)
+  if (NOT OSX_SDK_DIR) # Probably a Command Line Tools setup
+    set(OSX_SDK_DIR "/")
+  endif()
   if (IOSSIM_SDK_DIR AND NOT MACOSX_VERSION_MIN_FLAG)
     list(APPEND SANITIZER_COMMON_SUPPORTED_DARWIN_OS iossim)
   endif()
Index: make/platform/clang_darwin.mk
===================================================================
--- make/platform/clang_darwin.mk
+++ make/platform/clang_darwin.mk
@@ -64,6 +64,9 @@
 DSYMUTIL := $(call XCRun,dsymutil)
 
 OSX_SDK := $(call XCRunSdkPath,macosx)
+ifeq ($(OSX_SDK),)
+OSX_SDK := /
+endif
 IOS_SDK := $(call XCRunSdkPath,iphoneos)
 IOSSIM_SDK := $(call XCRunSdkPath,iphonesimulator)