Base-Toolchain: optimize option O2 -> Os

Base-Toolchain: optimize option O2 -> Os

Binary size and performance need to be evaluated with the change.

-Os
Optimize for size. -Os enables all -O2 optimizations except those that
often increase code size:

-falign-functions  -falign-jumps
-falign-labels  -falign-loops
-fprefetch-loop-arrays  -freorder-blocks-algorithm=stc

It also enables -finline-functions, causes the compiler to tune for code
size rather than execution speed, and performs further optimizations
designed to reduce code size.

Change-Id: I5d7d0ebfa3f0d311439e0b67aa3def8e02fc52c6
Signed-off-by: Dongkyun Son <dongkyun.s@samsung.com>