Update run_tests and examples makefile for scalar target.

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

tests/reduce-equal-4.ispc

@@ -2,7 +2,7 @@
 export uniform int width() { return programCount; }
 
 export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
-    int a = aFOO[programIndex/(programCount/2)];
+    int a = aFOO[programIndex/max(1, (programCount/2))];
     RET[programIndex] = 0;
     if (programIndex >= programCount/2 && a < 4)
         RET[programIndex] = reduce_equal(a) ? 1 : 0;