RIOT-OS/RIOT — pull request #1927 by kaspar030 (2014-11-03 11:23:48+00:00)
Title: make: optionally build with gcc's link time optimization

This commit enables building using link time optimization when
specifying "LTO=yes" in the application's Makefile (or compile with LTO=yes make ...).

Size comparisions:
| | native w/o lto | native w lto | msba2 w/o lto | msba2 w lto |
|-------------|----------------|--------------|---------------|-------------|
| hello_world | 29814 | 24817 | 48332 | 43948 |
| default | 71171 | 59282 | 118448 | 107108 |

Tested only with native and msba2.
On msba2, the syscalls needed __attribute__(used), causing default to use 16byte more in .text when not using LTO.