Fix libc++ headers for older macOS SDKs

Author: tresf

CMakeLists.txt

@@ -52,11 +52,21 @@ if(APPLE)
 		find_path(IOKit_INCLUDE_DIR NAMES IOKitLib.h HINTS ${IOKit_INC_SEARCH_PATH} ${IOKit_PKGC_INCLUDE_DIRS} PATH_SUFFIXES IOKit)
 		list(APPEND JSSC_ADDITIONAL_INCLUDES ${IOKit_INCLUDE_DIR})
 	endif()
+	# Handle edge-case with legacy versioned SDK headers (e.g. usr/include/c++/4.2.1)
+	if(CMAKE_OSX_SYSROOT)
+	    file(GLOB std_versions "${CMAKE_OSX_SYSROOT}/usr/include/c++/*")
+	    foreach(std_version IN LISTS std_versions)
+	        if("${std_version}" MATCHES "/v[0-9]*$")
+	             # Ignore c++/v1 (should already be included)
+	            continue()
+	        elseif(IS_DIRECTORY "${std_version}")
+	            message(STATUS "Adding legacy include path: ${std_version}")
+	            list(APPEND JSSC_ADDITIONAL_INCLUDES "${std_version}")
+	        endif()
+        endforeach()
+	endif()
 endif()
 
-set(CMAKE_CXX_STANDARD 11)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-
 # Statically link gcc/c++
 if(MSVC)
 	# /MT = Multithread, static version of the run-time library