[context] Split "env" values and prefixes.

recipe_modules/context/examples/full.expected/basic.json

Index: recipe_modules/context/examples/full.expected/basic.json
diff --git a/recipe_modules/context/examples/full.expected/basic.json b/recipe_modules/context/examples/full.expected/basic.json
index 27bbda653e68a19393e4a15ed1ebb53668922a6e..81fea77cbb6cc4dcbfdba8cb8242771abc3e0b43 100644
--- a/recipe_modules/context/examples/full.expected/basic.json
+++ b/recipe_modules/context/examples/full.expected/basic.json
@@ -59,9 +59,34 @@
       "echo $FOO"
     ],
     "env": {
-      "FOO": "[START_DIR]/pants:[START_DIR]/shirt:bar"
+      "FOO": "bar"
+    },
+    "env_prefixes": {
+      "FOO": [
+        "[START_DIR]/pants",
+        "[START_DIR]/shirt"
+      ]
+    },
+    "name": "env step with prefix",
+    "stdout": "/path/to/tmp/"
+  },
+  {
+    "cmd": [
+      "bash",
+      "-c",
+      "echo $FOO"
+    ],
+    "env": {
+      "FOO": ""
+    },
+    "env_prefixes": {
+      "FOO": [
+        "[START_DIR]/pants",
+        "[START_DIR]/shirt"
+      ]
     },
-    "name": "env step with prefix"
+    "name": "env prefixes with empty value",
+    "stdout": "/path/to/tmp/"
   },
   {
     "cmd": [],