Option 2:
If you are Hired any of Qatar Government offices or QP, Rasgas. No need of NOC letter. They will write a letter to that Company asking an NOC for you...Unless you donot have any bad records from your Previous Employer.....

Read more: http://www.qatarliving.com/node/1351524#ixzz10wBMvLQR

As stated by Bal-Samo;;;;;;it is not correct. Nobody even QP or Ras Gas or Qatar Gas, even the Government can force any company to give NOC. It is totally upto the your present employer, if he want, can release you, otherwise, you have to be banned for two years.