libc/eglibc: Add option to optimize for size

Add an option to eglibc to optimize for size using -Os.

Signed-off-by: Richard Strand <richard.strand@icomera.com>

 # Compute IA-64-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }