Go: group BUILD and dbscheme generation target

go/gen.py

@@ -0,0 +1,24 @@
+import sys
+import pathlib
+import subprocess
+from python.runfiles import runfiles
+
+this = pathlib.Path(__file__).resolve()
+go_extractor_dir = this.parent / "extractor"
+go_dbscheme = this.parent / "ql" / "lib" / "go.dbscheme"
+r = runfiles.Create()
+gazelle, go_gen_dbscheme = map(r.Rlocation, sys.argv[1:])
+
+print("clearing generated BUILD files")
+for build_file in go_extractor_dir.glob("*/**/BUILD.bazel"):
+    build_file.unlink()
+
+print("running gazelle")
+subprocess.check_call([gazelle, "go/extractor"])
+
+print("adding header to generated BUILD files")
+for build_file in go_extractor_dir.glob("*/**/BUILD.bazel"):
+    contents = build_file.read_text()
+    build_file.write_text(f"# generated running `bazel run //go/gazelle`, do not edit\n\n{contents}")
+
+subprocess.check_call([go_gen_dbscheme, go_dbscheme])