Change the host_debug sky_shell used for testing to build with assertions enabled

scripts/slave/recipes/flutter/engine.expected/linux.json

Index: scripts/slave/recipes/flutter/engine.expected/linux.json
diff --git a/scripts/slave/recipes/flutter/engine.expected/linux.json b/scripts/slave/recipes/flutter/engine.expected/linux.json
index 4a6f9bf7616cc9f6abfb7f0d7359724dfbedf6bd..3df413a166f86a6dadcf76b750fab49c5ebc1749 100644
--- a/scripts/slave/recipes/flutter/engine.expected/linux.json
+++ b/scripts/slave/recipes/flutter/engine.expected/linux.json
@@ -136,23 +136,24 @@
   },
   {
     "cmd": [
-      "[SLAVE_BUILD]/src/flutter/tools/gn"
+      "[SLAVE_BUILD]/src/flutter/tools/gn",
+      "--unoptimized"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/dart-sdk/dart-sdk/bin:%(PATH)s"
     },
-    "name": "gn "
+    "name": "gn --unoptimized (2)"

[eseidel, 2016/08/19 19:44:40]

When names are not unique they get (2) appended, etc.  This can be worked around
by explicitly naming the step when calling api.step, which RunGN does under the
covers I'm sure.

   },
   {
     "cmd": [
       "ninja",
       "-C",
-      "[SLAVE_BUILD]/src/out/host_debug"
+      "[SLAVE_BUILD]/src/out/host_debug_unopt"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/dart-sdk/dart-sdk/bin:%(PATH)s"
     },
-    "name": "build host_debug"
+    "name": "build host_debug_unopt"
   },
   {
     "cmd": [
@@ -164,7 +165,7 @@
       "PATH": "[SLAVE_BUILD]/src/third_party/dart-sdk/dart-sdk/bin:%(PATH)s"
     },
     "name": "Zip linux-x64 artifacts.zip",
-    "stdin": "{\"entries\": [{\"archive_name\": \"icudtl.dat\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug/icudtl.dat\", \"type\": \"file\"}, {\"archive_name\": \"sky_shell\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug/sky_shell\", \"type\": \"file\"}, {\"archive_name\": \"sky_snapshot\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug/sky_snapshot\", \"type\": \"file\"}], \"output\": \"[TMP_BASE]/tmp_tmp_1/artifacts.zip\", \"root\": \"[SLAVE_BUILD]/src\"}"
+    "stdin": "{\"entries\": [{\"archive_name\": \"icudtl.dat\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug_unopt/icudtl.dat\", \"type\": \"file\"}, {\"archive_name\": \"sky_shell\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug_unopt/sky_shell\", \"type\": \"file\"}, {\"archive_name\": \"sky_snapshot\", \"path\": \"[SLAVE_BUILD]/src/out/host_debug_unopt/sky_snapshot\", \"type\": \"file\"}], \"output\": \"[TMP_BASE]/tmp_tmp_1/artifacts.zip\", \"root\": \"[SLAVE_BUILD]/src\"}"
   },
   {
     "cmd": [
@@ -212,7 +213,7 @@
     "cmd": [
       "dart",
       "[SLAVE_BUILD]/src/flutter/sky/shell/testing/observatory/test.dart",
-      "[SLAVE_BUILD]/src/out/host_debug/sky_shell",
+      "[SLAVE_BUILD]/src/out/host_debug_unopt/sky_shell",
       "[SLAVE_BUILD]/src/flutter/sky/shell/testing/observatory/empty_main.dart"
     ],
     "cwd": "[SLAVE_BUILD]/src",