Command line support

Hi Longyi,

First of all, thanks for this awesome OCLint suite.
I made a small modification to the oclint-xcodebuild python script to make it accept the location of the xcodebuild.log file from command line parameter. With this the tool is able to generate the compile_commands.json in a different directory than the log file's.

If you have any questions, im all up to discussions.

Cheers,
Levend