How to change the pgsql source code and build it??

Hello,
I need to initialize the db as the root and start the database server. In
order to accomplish this, I modified the initdb.c source file of pgsql
package and tried to compile it. Eventhough the build was successful, I
couldn't see the root user able to execute initdb executable generated by
the build. I wanted to know if there is any other procedure for building
the postgresql procedure?

Thanks
Shreesha.

P.S
Below is the changes done in initdb.c (shown in bold letters below)