I am trying to determine if httpd is from the rpm or a custom build.
httpd -v
returns
Server version: Apache/2.2.15 (Unix)
Server built: Mar 3 2015 12:06:14
You can use rpm -qa
and/or yum list installed
to get a list of the installed packages.
rpm -qa httpd
or
yum list installed httpd
If the relevant httpd package isn't installed then you httpd was definitely compiled.
The above would determine if a relevant package had been installed but wouldn't help if a binary had later been compiled and then used to overwrite the original.
You can verify the files from an rpm
rpm -V httpd
this would tell you if files in the httpd package had changed since being installed.