创建，添加sdram

rt-thread/components/libc/posix/ipc/SConscript

@@ -0,0 +1,20 @@
+from building import *
+
+cwd        = GetCurrentDir()
+src        = []
+inc        = [cwd]
+
+# We have't implement of 'systemv ipc', so hide it firstly.
+# if GetDepend('RT_USING_POSIX_IPC_SYSTEM_V'):
+#     src += Glob('system-v/*.c')
+#     inc += [cwd + '/system-v']
+
+if GetDepend(['RT_USING_POSIX_MESSAGE_QUEUE', 'RT_USING_DFS_MQUEUE']):
+    src += ['mqueue.c']
+
+if GetDepend('RT_USING_POSIX_MESSAGE_SEMAPHORE'):
+    src += ['semaphore.c']
+
+group = DefineGroup('POSIX', src, depend = [''], CPPPATH = inc)
+
+Return('group')