Subzero: Fix the cmake build.
Subzero: Fix the cmake build.

BUG= none
R=mtrofin@chromium.org

Review URL: https://codereview.chromium.org/1041303002

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader