tests: Get builtin_compile to skin properly on pyboard.

tests/basics/builtin_compile.py

 # test compile builtin
 
+def have_compile():
     try:
         compile
+        return True
     except NameError:
-    print("SKIP")
-    import sys
-    sys.exit()
+        return False
+
+# global variable for compiled code to access
+x = 1
 
+def test():
     c = compile("print(x)", "file", "exec")
 
     try:
@@ -14,8 +18,12 @@ try:
     except NameError:
         print("NameError")
 
-x = 1
     exec(c)
 
     exec(c, {"x":2})
     exec(c, {}, {"x":3})
+
+if have_compile():
+    test()
+else:
+    print("SKIP")