Add BLAKE3 source code to third_party

Partial commit for third_party/*, see #18682.

Signed-off-by: Sunil Gowroji <sgowroji@google.com>

third_party/blake3/blake3.BUILD

@@ -0,0 +1,83 @@
+load("@rules_license//rules:license.bzl", "license")
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
+
+licenses(["notice"])  #  BSD/MIT-like license
+
+exports_files(["LICENSE"])
+
+license(
+    name = "license",
+    package_name = "blake3",
+    license_kinds = [
+        "@rules_license//licenses/spdx:Apache-2.0",
+    ],
+    license_text = "LICENSE",
+    package_version = "1.3.3",
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+    visibility = ["//third_party:__pkg__"],
+)
+
+cc_library(
+    name = "blake3",
+    srcs = [
+        "c/blake3.c",
+        "c/blake3_dispatch.c",
+        "c/blake3_portable.c",
+    ] + select({
+        "@bazel_tools//src/conditions:linux_x86_64": [
+            "c/blake3_avx2_x86-64_unix.S",
+            "c/blake3_avx512_x86-64_unix.S",
+            "c/blake3_sse2_x86-64_unix.S",
+            "c/blake3_sse41_x86-64_unix.S",
+        ],
+        "@bazel_tools//src/conditions:windows_x64": [
+            "c/blake3_avx2_x86-64_windows_msvc.asm",
+            "c/blake3_avx512_x86-64_windows_msvc.asm",
+            "c/blake3_sse2_x86-64_windows_msvc.asm",
+            "c/blake3_sse41_x86-64_windows_msvc.asm",
+        ],
+        "@bazel_tools//src/conditions:darwin_arm64": [
+            "c/blake3_neon.c",
+        ],
+        "//conditions:default": [],
+    }),
+    hdrs = [
+        "c/blake3.h",
+        "c/blake3_impl.h",
+    ],
+    copts = select({
+        "@bazel_tools//src/conditions:linux_x86_64": [],
+        "@bazel_tools//src/conditions:windows_x64": [],
+        "@bazel_tools//src/conditions:darwin_arm64": [
+            "-DBLAKE3_USE_NEON=1",
+        ],
+        "//conditions:default": [
+            "-DBLAKE3_NO_SSE2",
+            "-DBLAKE3_NO_SSE41",
+            "-DBLAKE3_NO_AVX2",
+            "-DBLAKE3_NO_AVX512",
+        ],
+    }),
+    includes = ["."],
+    visibility = ["//visibility:public"],
+)
+
+cc_binary(
+    name = "example",
+    srcs = [
+        "c/example.c",
+    ],
+    copts = [
+        "-w",
+        "-O3",
+    ],
+    includes = ["."],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":blake3",
+    ],
+)