can you pls tell me you are not able to execute means what and if possible tell me steps are you following in programming .
In GNU toolchain you need to configure lot of the things PLL, MAM,Stacks for various modes , finally you should work in User mode.
Keil does all these things for you ...in its startup routine and it has very good peripheral simulator for LPC21xx you heck this using keil..
Eval version of keil for ARM is having 16K code limitation but code you are mensioning will be much smaller than it.
So use keil eval version. generate hex file .download it using LPC Flash ISP utility
and check it ..After this you can try it over GNU tool with doing all the configurations.