remove gcc LTO flag from Makefile
remove gcc LTO flag from Makefile

LTO flag (-flto) is introduced into gcc since version 4.5.
See https://gcc.gnu.org/gcc-4.5/changes.html
So, here removing the LTO flag to make it works with gcc 4.4.7.

Microsoft/ntttcp-for-linux,Microsoft/ntttcp-for-linux