Update run_tests and examples makefile for scalar target.

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

tests/test-129.ispc

@@ -4,10 +4,10 @@ export uniform int width() { return programCount; }
 
 export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
     float a = aFOO[programIndex];
-    RET[programIndex] = extract(a, (uniform int)b-3);
+    RET[programIndex] = extract(a, min((uniform int)b-3, programCount-1));
 }
 
 
 export void result(uniform float RET[]) {
-    RET[programIndex] = 3;
+    RET[programIndex] = (programCount == 1) ? 1 : 3;
 }