Although we only produce libraries, 'lib' is confusing as an output
directory. We already used 'out' for the CMake build.

Bug b/116336664
Bug b/29024574

Change-Id: I2bc1015a72100f81f734fc969a32e9f5a967e17c
Reviewed-on: https://swiftshader-review.googlesource.com/c/21228Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>