Fix build on arm64 Linux. (#83)

third_party/blake3/BUILD.bazel

@@ -11,10 +11,11 @@ licenses(["unencumbered"])  # Creative Commons CC0
 exports_files(["LICENSE"])
 
 config_setting(
-    name = "windows",
-    values = {
-        "cpu": "x64_windows",
-    },
+    name = "x86_64_windows",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:windows",
+    ],
 )
 
 cc_library(
@@ -24,13 +25,16 @@ cc_library(
         "c/blake3_dispatch.c",
         "c/blake3_portable.c",
     ] + select({
-        ":windows": [
+        ":x86_64_windows": [
             "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",
         ],
-        "//conditions:default": [
+        "@platforms//cpu:arm64": [
+            "c/blake3_neon.c",
+        ],
+        "@platforms//cpu:x86_64": [
             "c/blake3_avx2_x86-64_unix.S",
             "c/blake3_avx512_x86-64_unix.S",
             "c/blake3_sse2_x86-64_unix.S",