Fix the Linux build.

Change-Id: I2c06dbe89f8e079f690242cd97af6638087af593
Reviewed-on: https://swiftshader-review.googlesource.com/1394
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>