[Bazel] Add support for compatible_with and restricted_to (#5681)

* Add support for compatible_with and restricted_to

These attributes have been available in Bazel for years.  Pass them
through so the flatbuffer rules can be used with them.  They let you
constrain which target platform is used.

While we are here, fix gen_reflections to work with bazel.

* Add docs

build_defs.bzl

@@ -35,6 +35,8 @@ def flatbuffer_library_public(
         flatc_args = DEFAULT_FLATC_ARGS,
         reflection_name = "",
         reflection_visibility = None,
+        compatible_with = None,
+        restricted_to = None,
         output_to_bindir = False):
     """Generates code files for reading/writing the given flatbuffers in the requested language using the public compiler.
 
@@ -52,6 +54,11 @@ def flatbuffer_library_public(
         reflection binaries for the schemas.
       reflection_visibility: The visibility of the generated reflection Fileset.
       output_to_bindir: Passed to genrule for output to bin directory.
+      compatible_with: Optional, The list of environments this rule can be
+        built for, in addition to default-supported environments.
+      restricted_to: Optional, The list of environments this rule can be built
+        for, instead of default-supported environments.
+      output_to_bindir: Passed to genrule for output to bin directory.
 
 
     This rule creates a filegroup(name) with all generated source files, and
@@ -84,6 +91,8 @@ def flatbuffer_library_public(
         output_to_bindir = output_to_bindir,
         tools = [flatc_path],
         cmd = genrule_cmd,
+        compatible_with = compatible_with,
+        restricted_to = restricted_to,
         message = "Generating flatbuffer files for %s:" % (name),
     )
     if reflection_name:
@@ -109,16 +118,17 @@ def flatbuffer_library_public(
             outs = reflection_outs,
             output_to_bindir = output_to_bindir,
             tools = [flatc_path],
+            compatible_with = compatible_with,
+            restricted_to = restricted_to,
             cmd = reflection_genrule_cmd,
             message = "Generating flatbuffer reflection binary for %s:" % (name),
         )
-        native.Fileset(
-            name = reflection_name,
-            out = "%s_out" % reflection_name,
-            entries = [
-                native.FilesetEntry(files = reflection_outs),
-            ],
+        native.filegroup(
+            name = "%s_out" % reflection_name,
+            srcs = reflection_outs,
             visibility = reflection_visibility,
+            compatible_with = compatible_with,
+            restricted_to = restricted_to,
         )
 
 def flatbuffer_cc_library(
@@ -130,6 +140,8 @@ def flatbuffer_cc_library(
         include_paths = DEFAULT_INCLUDE_PATHS,
         flatc_args = DEFAULT_FLATC_ARGS,
         visibility = None,
+        compatible_with = None,
+        restricted_to = None,
         srcs_filegroup_visibility = None,
         gen_reflections = False):
     '''A cc_library with the generated reader/writers for the given flatbuffer definitions.
@@ -153,6 +165,10 @@ 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.
+      compatible_with: Optional, The list of environments this rule can be built
+        for, in addition to default-supported environments.
+      restricted_to: Optional, The list of environments this rule can be built
+        for, instead of default-supported environments.
 
     This produces:
       filegroup([name]_srcs): all generated .h files.
@@ -208,6 +224,8 @@ def flatbuffer_cc_library(
         includes = includes,
         include_paths = include_paths,
         flatc_args = flatc_args,
+        compatible_with = compatible_with,
+        restricted_to = restricted_to,
         reflection_name = reflection_name,
         reflection_visibility = visibility,
     )
@@ -226,6 +244,8 @@ def flatbuffer_cc_library(
             "@com_github_google_flatbuffers//:runtime_cc",
         ],
         includes = [],
+        compatible_with = compatible_with,
+        restricted_to = restricted_to,
         linkstatic = 1,
         visibility = visibility,
     )
@@ -235,5 +255,7 @@ def flatbuffer_cc_library(
     native.filegroup(
         name = srcs_filegroup_name if srcs_filegroup_name else "%s_includes" % (name),
         srcs = srcs,
+        compatible_with = compatible_with,
+        restricted_to = restricted_to,
         visibility = srcs_filegroup_visibility if srcs_filegroup_visibility != None else visibility,
     )