Well, the true, absolutely 100% correct, but spectacularly unhelpful answer is "Install the rpm that has libXext.so in it."
Since you probably don't have any idea which package that is, it's not terribly helpful.
I don't have Mandrake 10.0 set up (I'm not even sure I've downloaded it), so I can't be certain of what package it might be in.
The library is referring to X extensions, so it's definitely going to be an X-related package.
My Gentoo box has it in "xfree", which is the basic XFree86 package. That argues it's one of the basic ones. (And causes me to be surprised you don't have it.)
My Red Hat box has in in "XFree86-libs-4.3.0-2" (Your version will very likely be at least a little different.)
So, my advice:
See if you have a package called XFree86-libs. If you do, see if it's installed....
I just thought of something else entirely. Do a "locate libXext.so". If you get something back, that means you DO have it, and you have a problem in Ogle's configuration. (Probably something like you'll have to pass it some info on what directories to look in for libraries.)
If "locate" doesn't exist, has problems, etc, you can do the same thing with "find / -name libXext.so".
Ok, now back to the idea that you DON'T have it. We were looking to see if there were any packages named something like XFree86-libs. If you find any, run "rpm -ql <package name>" and grep the output for the library.
Basically, you keep doing that with every package that looks like it might have something to do with it until you find the file. A post on the Mandrake board might find somebody with it already installed, and they can tell you what package it's in.
One last note: If you've run out of already-installed packages, and need to see what's in the packages that are on the CD, you have to add the "-p" parameter, and you don't use the package name ("xyzapp" for instance), you use the file name "xyzapp-3.6.8-i386.rpm". For instance, if you mounted the CD on /cdrom, you might enter "rpm -qlp /cdrom/Mandrake/RPMS/xyzapp-3.6.8-i386.rpm | grep libXext.so". (Run it once without the "| grep..." to make sure you've got the rpm command right. It should give you a list of file names.)
If/when you find the package that has the file, install that package. You should then be able run your ogle compile. (Suggestion, though - see if you can find a pre-canned ogld on someplace like rpmfind.net. Might save you a lot of grief.)
Hope this helps,