Revert "[toolchain/eglibc} eglibc in fact can be built with -Os"

Compiling with -Os results in: "error: #error "glibc cannot be compiled without optimization"

Still, building with -Os is listed as feature in
<http://www.eglibc.org/features>:

""
Building with -Os
     EGLIBC supports building the library with compiler optimizing for size -Os instead of for speed -O2.
""

SVN-Revision: 27245