Update run_tests and examples makefile for scalar target.

Fixed a number of tests that didn't handle the programCount == 1
case correctly.

tests/broadcast.ispc

@@ -3,7 +3,7 @@ export uniform int width() { return programCount; }
 
 export void f_f(uniform float RET[], uniform float aFOO[]) {
     float a = aFOO[programIndex]; 
-    float b = broadcast(a, 2);
+    float b = (programCount == 1) ? 3 : broadcast(a, 2);
     RET[programIndex] = b;
 }