Add builder_spec.py

Works like dm_flags.py and nanobench_flags.py; adds things like
GYP_DEFINES, additional environment variables, and build targets.

Required copying builder_name_schema from the tools/build repo.

BUG=skia:4132

Review URL: https://codereview.chromium.org/1265623002
diff --git a/tools/builder_name_schema.json b/tools/builder_name_schema.json
new file mode 100644
index 0000000..cffe9bf
--- /dev/null
+++ b/tools/builder_name_schema.json
@@ -0,0 +1,40 @@
+{
+  "builder_name_schema": {
+    "Test": [
+      "os",
+      "compiler",
+      "model",
+      "cpu_or_gpu",
+      "cpu_or_gpu_value",
+      "arch",
+      "configuration"
+    ],
+    "Housekeeper": [
+      "frequency"
+    ],
+    "Build": [
+      "os",
+      "compiler",
+      "target_arch",
+      "configuration"
+    ],
+    "Perf": [
+      "os",
+      "compiler",
+      "model",
+      "cpu_or_gpu",
+      "cpu_or_gpu_value",
+      "arch",
+      "configuration"
+    ],
+    "Canary": [
+      "project",
+      "os",
+      "compiler",
+      "target_arch",
+      "configuration"
+    ]
+  },
+  "builder_name_sep": "-",
+  "trybot_name_suffix": "Trybot"
+}