Modify the file main.cpp for M487

Revision:
0:0dfa64725959
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Fri Sep 29 05:44:18 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#ca661f9d28526ca8f874b05432493a489c9671ea