Update BUILD

Change all the instances of "darwin" to "osx" to be consistent.

toolchain/BUILD

@@ -105,7 +105,7 @@ cc_toolchain_config(
 )
 
 cc_toolchain_config(
-    name = "darwin-aarch_64-config",
+    name = "osx-aarch_64-config",
     bit_flag = "-m64",
     cpp_flag = "-lc++",
     include_flag = [
@@ -117,11 +117,11 @@ cc_toolchain_config(
     target_cpu = "aarch64",
     target_full_name = "aarch64-apple-macosx11.3",
     toolchain_dir = "/usr/tools/apple_sdks/xcode_13_0/macosx",
-    toolchain_name = "darwin_aarch_64",
+    toolchain_name = "osx_aarch_64",
 )
 
 cc_toolchain_config(
-    name = "darwin-x86_64-config",
+    name = "osx-x86_64-config",
     bit_flag = "-m64",
     cpp_flag = "-lc++",
     include_flag = [
@@ -133,5 +133,5 @@ cc_toolchain_config(
     target_cpu = "x86_64",
     target_full_name = "x86_64-apple-macosx11.3",
     toolchain_dir = "/usr/tools/apple_sdks/xcode_13_0/macosx",
-    toolchain_name = "darwin_x86_64",
+    toolchain_name = "osx_x86_64",
 )