/usr/share is being owned by glibc:

$ rpm -qlp -vv glibc-2.2-5.fixarch.i686.rpm
...
drwxr-xr-x    1 root    root             4096 Nov 22 02:39 /usr/share


(Because rpm is buggy, cpio will fail if /usr/shared is %netshared and
mounted ro. So installation of glibc gets incomplete)

No other package (except filesystem) owns /usr/share so it seems to be a
bug in glibc.

I think the statement
-----------------
for n in %{_prefix}/share %{_prefix}/include %{_prefix}/lib/locale; do 
    find ${RPM_BUILD_ROOT}${n} -type d | \
        grep -v '^%{_prefix}/share$' | \
        sed "s/^/%dir /" >> rpm.filelist.in
done
-----------------

in glibc.spec is wrong. You are grep'ping for directories *beginning* (^)
with /usr/share, but
`find' returns $RPM_BUILD_ROOT/usr/share.