Moved selection of I915 hack out of the YUV shader.

client/deps/glbench/src/yuv2rgb_2.glslv

 uniform float imageHeight;
 
 attribute vec4 c;
 
-#define I915_WORKAROUND 1
-
 varying vec2 lineCounter;
 varying vec2 yPlane;
 varying vec2 uPlane;
 varying vec2 vPlane;
 
 void main() {
   gl_Position = c;
-#if I915_WORKAROUND
+#if defined(I915_WORKAROUND)
   gl_TexCoord[0].xy = vec2(c.y * imageHeight / 4.0, 0.0);
   gl_TexCoord[0].zw = vec2(c.x, (2.0 * c.y + 1.0) / 3.0);
   gl_TexCoord[1].xy = vec2(c.x / 2.0, (c.y + 1.0) / 6.0);
   gl_TexCoord[1].zw = vec2(c.x / 2.0, c.y / 6.0);
 #else
   lineCounter = vec2(c.y * imageHeight / 4.0, 0.0);
   yPlane = vec2(c.x, (2.0 * c.y + 1.0) / 3.0);
   uPlane = vec2(c.x / 2.0, (c.y + 1.0) / 6.0);
   vPlane = vec2(c.x / 2.0, c.y / 6.0);
 #endif
 }