GN: expunge all environment variables that have no effect on GN

infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json

Index: infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json b/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
index 1472cb72af5cd01f84cd5a7836a0c6e89517d1eb..3408d76c16c871b53d257824ef79063939109b4c 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
@@ -80,11 +80,7 @@
     ],
     "cwd": "[CUSTOM_C:\\_B_WORK]\\skia",
     "env": {
-      "BUILDTYPE": "Release",
-      "CHROME_HEADLESS": "1",
-      "GYP_DEFINES": "qt_sdk=C:/Qt/4.8.5/ skia_arch_type=x86 skia_warnings_as_errors=1 skia_win_debuggers_path=c:/DbgHelp skia_win_ltcg=0",
-      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_C:\\_B_WORK]\\skia\\out\\Build-Win-MSVC-x86-Release-GN"
+      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "fetch-gn"
   },
@@ -97,11 +93,7 @@
     ],
     "cwd": "[CUSTOM_C:\\_B_WORK]\\skia",
     "env": {
-      "BUILDTYPE": "Release",
-      "CHROME_HEADLESS": "1",
-      "GYP_DEFINES": "qt_sdk=C:/Qt/4.8.5/ skia_arch_type=x86 skia_warnings_as_errors=1 skia_win_debuggers_path=c:/DbgHelp skia_win_ltcg=0",
-      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_C:\\_B_WORK]\\skia\\out\\Build-Win-MSVC-x86-Release-GN"
+      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gn gen"
   },
@@ -113,11 +105,7 @@
     ],
     "cwd": "[CUSTOM_C:\\_B_WORK]\\skia",
     "env": {
-      "BUILDTYPE": "Release",
-      "CHROME_HEADLESS": "1",
-      "GYP_DEFINES": "qt_sdk=C:/Qt/4.8.5/ skia_arch_type=x86 skia_warnings_as_errors=1 skia_win_debuggers_path=c:/DbgHelp skia_win_ltcg=0",
-      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_C:\\_B_WORK]\\skia\\out\\Build-Win-MSVC-x86-Release-GN"
+      "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools];RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "ninja"
   },