If you have the required dev tools installed on the Galileo, you can compile the i2c tools from the source on the Galileo.
But before compile&install you have to patch a single line in py-smbus/smbusmodule.c. There is a constant named I2C_SLAVE but the constant I2C_SLAVE_FORCE is required.
After doing this, I was able to use the SMBus extension in Python without any problems.