[add] posix testcase frame. (#6127)

examples/utest/testcases/posix/SConscript

@@ -0,0 +1,14 @@
+import os
+Import('RTT_ROOT')
+from building import *
+
+cwd = GetCurrentDir()
+objs = []
+list = os.listdir(cwd)
+
+for d in list:
+    path = os.path.join(cwd, d)
+    if os.path.isfile(os.path.join(path, 'SConscript')):
+        objs = objs + SConscript(os.path.join(d, 'SConscript'))
+
+Return('objs')