Bazel ci (#5228)

* Stop building for Windows until the build passes

ERROR: D:/b/bk-windows-java8-bd0z/bazel/flatbuffers/BUILD:123:1: Couldn't build file _objs/flatbuffers_test/test.obj: undeclared inclusion(s) in rule '//:flatbuffers_test':
this rule is missing dependency declarations for the following files included by 'tests/test.cpp':
  'tests/monster_test_generated.h'
  'tests/monster_extra_generated.h'

The files in tests are being found instead of the generated files since
Windows doesn't have any sandboxing.  For now, let's disable the rules
and come back to it.

* Fix buildifier warnings

Clean up docstrings and add a module docstring.

.bazelci/presubmit.yml

@@ -16,8 +16,3 @@ platforms:
     - "..."
     test_targets:
     - "..."
-  windows:
-    build_targets:
-    - "..."
-    test_targets:
-    - "..."

build_defs.bzl

@@ -1,6 +1,10 @@
 # Description:
 #   BUILD rules for generating flatbuffer files in various languages.
 
+"""
+Rules for building C++ flatbuffers with Bazel.
+"""
+
 flatc_path = "@com_github_google_flatbuffers//:flatc"
 
 DEFAULT_INCLUDE_PATHS = [
@@ -46,9 +50,11 @@ def flatbuffer_library_public(
         reflection binaries for the schemas.
       reflection_visiblity: The visibility of the generated reflection Fileset.
       output_to_bindir: Passed to genrule for output to bin directory.
-    Outs:
+
-      filegroup(name): all generated source files.
+
-      Fileset([reflection_name]): (Optional) all generated reflection binaries.
+    This rule creates a filegroup(name) with all generated source files, and
+    optionally a Fileset([reflection_name]) with all generated reflection
+    binaries.
     """
     include_paths_cmd = ["-I %s" % (s) for s in include_paths]
 
@@ -145,7 +151,8 @@ def flatbuffer_cc_library(
           By default, use the value of the visibility parameter above.
       gen_reflections: Optional, if true this will generate the flatbuffer
         reflection binaries for the schemas.
-    Outs:
+
+    This produces:
       filegroup([name]_srcs): all generated .h files.
       filegroup(srcs_filegroup_name if specified, or [name]_includes if not):
           Other flatbuffer_cc_library's can pass this in for their `includes`