recipe engine: extract infra-specific paths out of the engine

recipe_modules/path/example.expected/linux.json

Index: recipe_modules/path/example.expected/linux.json
diff --git a/recipe_modules/path/example.expected/linux.json b/recipe_modules/path/example.expected/linux.json
index fdfa97805a71e4edc36e64beecde60f8676a32e0..5f73f748eeeb7f62e1e878a0a7a91763df7335b5 100644
--- a/recipe_modules/path/example.expected/linux.json
+++ b/recipe_modules/path/example.expected/linux.json
@@ -2,9 +2,8 @@
   {
     "cmd": [
       "/bin/echo",
-      "[SLAVE_BUILD]/foo"
+      "[TMP_BASE]/foo"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "step1"
   },
   {
@@ -12,7 +11,6 @@
       "echo",
       "RECIPE_MODULE[recipe_engine::path]/resources/dir/file.py"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print resource"
   },
   {
@@ -20,23 +18,20 @@
       "echo",
       "RECIPE_PACKAGE_REPO[recipe_engine]/dir/file.py"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print package dir"
   },
   {
     "cmd": [
       "/bin/echo",
-      "[SLAVE_BUILD]/checkout/jerky"
+      "[TMP_BASE]/checkout/jerky"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "checkout path"
   },
   {
     "cmd": [
       "touch",
-      "[SLAVE_BUILD]/new_file"
+      "[TMP_BASE]/new_file"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "touch me"
   },
   {