Update flatbuffers.

Use upstream flatbuffer bazel scripts, with a couple of small patches to fix:
* google/flatbuffers#8087 (remove npm references)
* google/flatbuffers#8088 (fix flatc build failure due to main() removal by linker)

jaxlib/cpu/BUILD

@@ -79,7 +79,7 @@ cc_library(
         ":ducc_fft_flatbuffers_cc",
         "@xla//xla/service:custom_call_status",
         "@ducc",
-        "@flatbuffers//:runtime_cc",
+        "@com_github_google_flatbuffers//:flatbuffers",
     ],
 )
 
@@ -96,7 +96,7 @@ pybind_extension(
         ":ducc_fft_flatbuffers_cc",
         ":ducc_fft_kernels",
         "//jaxlib:kernel_nanobind_helpers",
-        "@flatbuffers//:runtime_cc",
+        "@com_github_google_flatbuffers//:flatbuffers",
         "@nanobind",
     ],
 )

jaxlib/jax.bzl

@@ -14,12 +14,12 @@
 
 """Bazel macros used by the JAX build."""
 
-load("@tsl//tsl:tsl.bzl", _if_windows = "if_windows", _pybind_extension = "tsl_pybind_extension_opensource")
+load("@com_github_google_flatbuffers//:build_defs.bzl", _flatbuffer_cc_library = "flatbuffer_cc_library")
 load("@local_config_cuda//cuda:build_defs.bzl", _cuda_library = "cuda_library", _if_cuda_is_configured = "if_cuda_is_configured")
 load("@local_config_rocm//rocm:build_defs.bzl", _if_rocm_is_configured = "if_rocm_is_configured", _rocm_library = "rocm_library")
-load("@flatbuffers//:build_defs.bzl", _flatbuffer_cc_library = "flatbuffer_cc_library")
-load("@tsl//tsl/platform:build_config_root.bzl", _tf_cuda_tests_tags = "tf_cuda_tests_tags", _tf_exec_properties = "tf_exec_properties")
 load("@rules_cc//cc:defs.bzl", _cc_proto_library = "cc_proto_library")
+load("@tsl//tsl:tsl.bzl", _if_windows = "if_windows", _pybind_extension = "tsl_pybind_extension_opensource")
+load("@tsl//tsl/platform:build_config_root.bzl", _tf_cuda_tests_tags = "tf_cuda_tests_tags", _tf_exec_properties = "tf_exec_properties")
 
 # Explicitly re-exports names to avoid "unused variable" warnings from .bzl
 # lint tools.