[OT] Strings embedded by gcc in executables?

[walt]

I know that one of you compiler geeks will know the answer
to this puzzle:

When doing a 'strings -a <binaryexecutable>' I usually see
the footprint left by the version of gcc which compiled the
program.

For example:

$strings -a firefox-bin | grep GCC
GCC: (GNU) 3.3.6 (Gentoo 3.3.6, ssp-3.3.6-1.0, pie-8.7.8)
[many identical lines snipped]

My question is:  under what conditions would two different
such compiler version-strings appear in *one* executable file?

The obvious corollary is:  why does gcc leave such version-
stamps in a file in the first place?

Any wisdom you could impart would be much appreciated.

Thanks!