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

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.
""

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@27245 3c298f89-4303-0410-b956-a3cf2f4a3e73