Change Permissions on Linux x86_64

[Paul McQuade]

Change the permissions on p2bin to compile sonic 1.

Before:

lua build.lua 
Uncompressed driver size: 1BC6h bytes.
sh: line 1: build_tools/Linux-x86_64/p2bin: Permission denied

After:

lua build.lua 
Uncompressed driver size: 1BC6h bytes.