Add initial Bazel WORKSPACE and BUILD (#4608)

For #4574.

To test:

    bazel test --verbose_failures //:flatbuffers_test

.gitignore

@@ -81,4 +81,9 @@ android/build/
 samples/android/.externalNativeBuild/
 samples/android/.gradle/
 samples/android/build/
-js/flatbuffers.mjs
\ No newline at end of file
+js/flatbuffers.mjs
+/bazel-bin
+/bazel-flatbuffers
+/bazel-genfiles
+/bazel-out
+/bazel-testlogs
\ No newline at end of file

BUILD

+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "-layering_check",
+        "-parse_headers",
+    ],
+)
+
+exports_files([
+    "LICENSE",
+])
+
+FLATBUFFERS_COPTS = [
+    "-Wno-implicit-fallthrough",
+    "-linclude",
+]
+
+# Public flatc library to compile flatbuffer files at runtime.
+cc_library(
+    name = "flatbuffers",
+    srcs = [
+        "src/code_generators.cpp",
+        "src/idl_gen_fbs.cpp",
+        "src/idl_gen_general.cpp",
+        "src/idl_gen_text.cpp",
+        "src/idl_parser.cpp",
+        "src/reflection.cpp",
+        "src/util.cpp",
+    ],
+    hdrs = [":public_headers"],
+    copts = FLATBUFFERS_COPTS,
+    includes = ["include/"],
+    linkstatic = 1,
+)
+
+# Public C++ headers for the Flatbuffers library.
+filegroup(
+    name = "public_headers",
+    srcs = [
+        "include/flatbuffers/base.h",
+        "include/flatbuffers/code_generators.h",
+        "include/flatbuffers/flatbuffers.h",
+        "include/flatbuffers/flexbuffers.h",
+        "include/flatbuffers/hash.h",
+        "include/flatbuffers/idl.h",
+        "include/flatbuffers/reflection.h",
+        "include/flatbuffers/reflection_generated.h",
+        "include/flatbuffers/stl_emulation.h",
+        "include/flatbuffers/util.h",
+    ],
+)
+
+# Public flatc compiler library.
+cc_library(
+    name = "flatc_library",
+    srcs = [
+        "src/code_generators.cpp",
+        "src/flatc.cpp",
+        "src/idl_gen_fbs.cpp",
+        "src/idl_parser.cpp",
+        "src/reflection.cpp",
+        "src/util.cpp",
+    ],
+    hdrs = [
+        "include/flatbuffers/flatc.h",
+        ":public_headers",
+    ],
+    copts = FLATBUFFERS_COPTS,
+    includes = [
+        "grpc/",
+        "include/",
+    ],
+)
+
+# Public flatc compiler.
+cc_binary(
+    name = "flatc",
+    srcs = [
+        "grpc/src/compiler/config.h",
+        "grpc/src/compiler/cpp_generator.cc",
+        "grpc/src/compiler/cpp_generator.h",
+        "grpc/src/compiler/go_generator.cc",
+        "grpc/src/compiler/go_generator.h",
+        "grpc/src/compiler/schema_interface.h",
+        "src/flatc_main.cpp",
+        "src/idl_gen_cpp.cpp",
+        "src/idl_gen_general.cpp",
+        "src/idl_gen_go.cpp",
+        "src/idl_gen_grpc.cpp",
+        "src/idl_gen_js.cpp",
+        "src/idl_gen_json_schema.cpp",
+        "src/idl_gen_php.cpp",
+        "src/idl_gen_python.cpp",
+        "src/idl_gen_text.cpp",
+    ],
+    copts = FLATBUFFERS_COPTS,
+    includes = [
+        "grpc/",
+        "include/",
+    ],
+    deps = [
+        ":flatc_library",
+    ],
+)
+
+# Test binary.
+cc_test(
+    name = "flatbuffers_test",
+    testonly = 1,
+    srcs = [
+        "include/flatbuffers/minireflect.h",
+        "include/flatbuffers/registry.h",
+        "src/code_generators.cpp",
+        "src/idl_gen_fbs.cpp",
+        "src/idl_gen_general.cpp",
+        "src/idl_gen_text.cpp",
+        "src/idl_parser.cpp",
+        "src/reflection.cpp",
+        "src/util.cpp",
+        "tests/monster_test_generated.h",
+        "tests/namespace_test/namespace_test1_generated.h",
+        "tests/namespace_test/namespace_test2_generated.h",
+        "tests/test.cpp",
+        "tests/union_vector/union_vector_generated.h",
+        ":public_headers",
+    ],
+    copts = FLATBUFFERS_COPTS + [
+        "-DFLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE",
+    ],
+    data = [
+        ":tests/include_test/include_test1.fbs",
+        ":tests/include_test/sub/include_test2.fbs",
+        ":tests/monster_test.bfbs",
+        ":tests/monster_test.fbs",
+        ":tests/monsterdata_test.golden",
+        ":tests/prototest/imported.proto",
+        ":tests/prototest/test.golden",
+        ":tests/prototest/test.proto",
+        ":tests/union_vector/union_vector.fbs",
+    ],
+    includes = ["include/"],
+)

WORKSPACE

+workspace(name = "com_github_google_flatbuffers")
+