[Compile perf] Make scale-test conditional on assertions, rdar://29090287

Author: graydon

validation-test/compiler_scale/scale_neighbouring_getset.gyb

@@ -1,5 +1,5 @@
 // RUN: %scale-test --sum-multi --parse --begin 5 --end 16 --step 5 --select typeCheckAbstractFunctionBody %s
-// REQUIRES: OS=macosx, tools-release
+// REQUIRES: OS=macosx, tools-release, assertions
 
 struct Struct${N} {
 % if int(N) > 1: