Fix compilation on Linux

src/libANGLE/Display.cpp

@@ -564,6 +564,7 @@ void Display::destroySurface(Surface *surface)
         }
 
         ASSERT(surfaceRemoved);
+        UNUSED_ASSERTION_VARIABLE(surfaceRemoved);
     }
 
     mImplementation->destroySurface(surface);

src/libANGLE/Program.cpp

@@ -1611,6 +1611,7 @@ bool Program::gatherTransformFeedbackLinkedVaryings(InfoLog &infoLog, const std:
 
         // All transform feedback varyings are expected to exist since packVaryings checks for them.
         ASSERT(found);
+        UNUSED_ASSERTION_VARIABLE(found);
     }
 
     if (transformFeedbackBufferMode == GL_INTERLEAVED_ATTRIBS &&