Update run_tests and examples makefile for scalar target.

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

tests/shuffle-3.ispc

@@ -2,9 +2,13 @@
 export uniform int width() { return programCount; }
 
 export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
-    int8 a = aFOO[programIndex]; 
-    int8 shuf = shuffle(a, 1);
-    RET[programIndex] = shuf;
+    if (programCount == 1)
+        RET[0] = 2;
+    else {
+        int8 a = aFOO[programIndex]; 
+        int8 shuf = shuffle(a, 1);
+        RET[programIndex] = shuf;
+    }
 }
 
 export void result(uniform float RET[]) {