Split Bazel targets into multiple packages (#5640)

* Split Bazel targets into multiple packages

* Merge /include/BUILD back into /BUILD

src/BUILD

@@ -0,0 +1,73 @@
+package(
+    default_visibility = ["//visibility:private"],
+)
+
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
+
+# Public flatc library to compile flatbuffer files at runtime.
+cc_library(
+    name = "flatbuffers",
+    srcs = [
+        "code_generators.cpp",
+        "idl_gen_fbs.cpp",
+        "idl_gen_text.cpp",
+        "idl_parser.cpp",
+        "reflection.cpp",
+        "util.cpp",
+    ],
+    hdrs = ["//:public_headers"],
+    strip_include_prefix = "/include",
+    visibility = ["//:__pkg__"],
+)
+
+# Public flatc compiler library.
+cc_library(
+    name = "flatc_library",
+    srcs = [
+        "flatc.cpp",
+    ],
+    hdrs = [
+        "//:flatc_headers",
+    ],
+    strip_include_prefix = "/include",
+    visibility = ["//:__pkg__"],
+    deps = [
+        ":flatbuffers",
+    ],
+)
+
+# Public flatc compiler.
+cc_library(
+    name = "flatc",
+    srcs = [
+        "flatc_main.cpp",
+        "idl_gen_cpp.cpp",
+        "idl_gen_csharp.cpp",
+        "idl_gen_dart.cpp",
+        "idl_gen_go.cpp",
+        "idl_gen_grpc.cpp",
+        "idl_gen_java.cpp",
+        "idl_gen_js_ts.cpp",
+        "idl_gen_json_schema.cpp",
+        "idl_gen_kotlin.cpp",
+        "idl_gen_lobster.cpp",
+        "idl_gen_lua.cpp",
+        "idl_gen_php.cpp",
+        "idl_gen_python.cpp",
+        "idl_gen_rust.cpp",
+        "idl_gen_text.cpp",
+        "util.cpp",
+    ],
+    hdrs = [
+        "//:flatc_headers",
+    ],
+    strip_include_prefix = "/include",
+    visibility = ["//:__pkg__"],
+    deps = [
+        ":flatc_library",
+        "//grpc/src/compiler:cpp_generator",
+        "//grpc/src/compiler:go_generator",
+        "//grpc/src/compiler:java_generator",
+        "//grpc/src/compiler:python_generator",
+    ],
+)