Fix compilation error on android build.

Fix compilation error on android build.

The error that appears when trying to build swiftshader master as part
of android is:
external/swiftshader/src/Shader/Shader.cpp:1886:51: error: expected '(' for function-style cast or type construction

Change-Id: I667f249e46ed99c3c598490182e495c0862c64a9
Reviewed-on: https://swiftshader-review.googlesource.com/c/23768
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Lingfeng Yang <lfy@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>