building libc - double compilations ?

[Metuki Sabhe]

hello list,

does the building process of libc involve two compilations for
some files (under different defines) ?

I specifically aim at the building of libc.a and libc-2.5.so.
are these just different packaging of the same objects or
does the build process actually recompile the files
(thus creating new objects) for each library type ?

thank you
metuki