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

recipe_modules/shutil/example.expected/basic.json

Index: recipe_modules/shutil/example.expected/basic.json
diff --git a/recipe_modules/shutil/example.expected/basic.json b/recipe_modules/shutil/example.expected/basic.json
index 58a06c26be206974b54679818f5307b6678c78c9..c369d78ebb259af2e33b15cbd9015367e060c359 100644
--- a/recipe_modules/shutil/example.expected/basic.json
+++ b/recipe_modules/shutil/example.expected/basic.json
@@ -6,7 +6,6 @@
       "\nimport os\nimport sys\nos.remove(sys.argv[1])\n",
       "bar"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "foo",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -24,7 +23,6 @@
       "/fake/dir",
       "/path/to/tmp/json"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "listdir fake dir",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@[@@@",
@@ -45,7 +43,6 @@
       "some",
       "command"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "manipulate file 1"
   },
   {
@@ -53,7 +50,6 @@
       "some",
       "command"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "manipulate file 2"
   },
   {
@@ -61,7 +57,6 @@
       "echo",
       "[TMP_BASE]/prefix_a_tmp_1"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print prefix_a"
   },
   {
@@ -69,7 +64,6 @@
       "echo",
       "[TMP_BASE]/prefix_b_tmp_2"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print prefix_b"
   },
   {
@@ -80,7 +74,6 @@
       "abcde",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_simple"
   },
   {
@@ -91,7 +84,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_simple"
   },
   {
@@ -102,7 +94,6 @@
       "! ~&&",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_symbols"
   },
   {
@@ -113,7 +104,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_symbols"
   },
   {
@@ -124,7 +114,6 @@
       "abcde fgh",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_spaces"
   },
   {
@@ -135,7 +124,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_spaces"
   },
   {
@@ -146,7 +134,6 @@
       "ab\ncd\nefg\n",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_multiline"
   },
   {
@@ -157,7 +144,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_multiline"
   },
   {
@@ -165,10 +151,9 @@
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
-      "[SLAVE_BUILD]/copytree_example_tmp",
+      "[TMP_BASE]/copytree_example_tmp",
       "511"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "makedirs makedirs",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -189,21 +174,19 @@
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "some file content",
-      "[SLAVE_BUILD]/copytree_example_tmp/dummy_file"
+      "[TMP_BASE]/copytree_example_tmp/dummy_file"
     ],
-    "cwd": "[SLAVE_BUILD]",
-    "name": "write [SLAVE_BUILD]/copytree_example_tmp/dummy_file"
+    "name": "write [TMP_BASE]/copytree_example_tmp/dummy_file"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copytree(sys.argv[1], sys.argv[2], symlinks=bool(sys.argv[3]))\n",
-      "[SLAVE_BUILD]/copytree_example_tmp",
-      "[SLAVE_BUILD]/copytree_example_tmp2",
+      "[TMP_BASE]/copytree_example_tmp",
+      "[TMP_BASE]/copytree_example_tmp2",
       "0"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "copytree"
   },
   {
@@ -211,11 +194,10 @@
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "[SLAVE_BUILD]/copytree_example_tmp2/dummy_file",
+      "[TMP_BASE]/copytree_example_tmp2/dummy_file",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
-    "name": "read [SLAVE_BUILD]/copytree_example_tmp2/dummy_file"
+    "name": "read [TMP_BASE]/copytree_example_tmp2/dummy_file"
   },
   {
     "cmd": [
@@ -223,9 +205,8 @@
       "-u",
       "\nimport glob\nimport sys\nwith open(sys.argv[1], 'w') as f:\n  f.write('\\n'.join(glob.glob(sys.argv[2])))\n",
       "/path/to/tmp/",
-      "[SLAVE_BUILD]/copytree_example_tmp/*"
+      "[TMP_BASE]/copytree_example_tmp/*"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "glob"
   },
   {
@@ -233,9 +214,8 @@
       "python",
       "-u",
       "\nimport shutil, sys\nshutil.rmtree(sys.argv[1])\n",
-      "[SLAVE_BUILD]/copytree_example_tmp"
+      "[TMP_BASE]/copytree_example_tmp"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -249,9 +229,8 @@
       "python",
       "-u",
       "\nimport shutil, sys\nshutil.rmtree(sys.argv[1])\n",
-      "[SLAVE_BUILD]/copytree_example_tmp2"
+      "[TMP_BASE]/copytree_example_tmp2"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup2",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",