diff --git a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
index 2abf053..91eb9b2 100644
--- a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
+++ b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
@@ -354,7 +354,9 @@
   optional bool supports_gold_linker = 10 [default = false];
   // Legacy field, ignored by Bazel.
   optional bool supports_thin_archives = 11 [default = false];
+  // Legacy field, use 'supports_start_end_lib' feature instead.
   optional bool supports_start_end_lib = 28 [default = false];
+  // Legacy field, use 'supports_interface_shared_libraries' instead.
   optional bool supports_interface_shared_objects = 32 [default = false];
   optional bool supports_embedded_runtimes = 40 [default = false];
   // If specified, Blaze finds statically linked / dynamically linked runtime
@@ -364,9 +366,9 @@
   optional string static_runtimes_filegroup = 45;
   // Deprecated, see https://github.com/bazelbuild/bazel/issues/6942
   optional string dynamic_runtimes_filegroup = 46;
+  // Legacy field, ignored by Bazel.
   optional bool supports_incremental_linker = 41 [default = false];
-  // This should be true, if the toolchain supports the D flag to ar, which
-  // makes it output normalized archives that don't contain timestamps.
+  // Legacy field, ignored by Bazel.
   optional bool supports_normalizing_ar = 26 [default = false];
   optional bool supports_fission = 43 [default = false];
   // Can generate dsym debug symbol information.
@@ -398,7 +400,7 @@
   repeated string ar_flag = 47;
   // Legacy field, ignored by Bazel.
   repeated string ar_thin_archives_flag = 48;
-  // Additional compiler flags that are added for cc_plugin rules of type 'gcc'
+  // Legacy field, ignored by Bazel.
   repeated string gcc_plugin_compiler_flag = 34;
 
   // Additional compiler and linker flags depending on the compilation mode.
@@ -407,10 +409,9 @@
   // Additional linker flags depending on the linking mode.
   repeated LinkingModeFlags linking_mode_flags = 18;
 
-  // Plugin header directories for gcc and mao plugins. If none are set, the
-  // toolchain does not support plugins. Relative paths are resolved relative
-  // to the configuration file directory.
+  // Legacy field, ignored by Bazel.
   repeated string gcc_plugin_header_directory = 19;
+  // Legacy field, ignored by Bazel.
   repeated string mao_plugin_header_directory = 20;
 
   // Make variables that are made accessible to rules.
@@ -435,15 +436,11 @@
   // see the documentation above.
   optional string builtin_sysroot = 24;
 
-  // The location and version of the default Python (in absence of
-  // --python_top and --python_version, respectively. The default
-  // --python_mode is always 'opt'.) For backward compatibility, if these
-  // attributes are not set, Blaze will use the crosstool v11-13 default
-  // values: "/usr/grte/v1" and "python2.4".
+  // Legacy field, ignored by Bazel.
   optional string default_python_top = 29;
+  // Legacy field, ignored by Bazel.
   optional string default_python_version = 30;
-  // Whether to preload swigdeps.so files in py_binaries and PAR files.
-  // This overrides the commandline flag.
+  // Legacy field, ignored by Bazel.
   optional bool python_preload_swigdeps = 42;
 
   // The default GRTE to use. This should be a label, and gets the same
@@ -456,13 +453,11 @@
   // This may only be set to a non-empty value if builtin_sysroot is also set!
   optional string default_grte_top = 31;
 
-  // Additional dependencies for Blaze-built .deb packages. All Debian packages
-  // that contain C++ binaries need to have the correct runtime
-  // libraries installed, and those depend on the crosstool version, which is
-  // why they are recorded here.
+  // Legacy field, ignored by Bazel.
   repeated string debian_extra_requires = 33;
 
-  // Unused, for compatibility with things internal to Google.
+  // Legacy field, ignored by Bazel. Only there for compatibility with
+  // things internal to Google.
   optional string cc_target_os = 55;
 
   // Next free id: 56
@@ -511,20 +506,16 @@
   required string toolchain_identifier = 2;
 }
 
-// An entire crosstool release, containing the version number, a default target
-// cpu, a default toolchain for each supported cpu type, and a set of
+// An entire crosstool release, containing the version number, and a set of
 // toolchains.
 message CrosstoolRelease {
   // The major and minor version of the crosstool release.
   required string major_version = 1;
   required string minor_version = 2;
 
-  // Deprecated. Used to be the default CPU if not otherwise specified, but it's
-  // not used for that purpose (or anything else) anymore. Please also don't add
-  // new uses of this field.
+  // Legacy field, ignored by Bazel.
   optional string default_target_cpu = 3;
-  // Deprecated: The default toolchain to use for each given cpu.
-  // Use cc_toolchain_suite.toolchains with only cpu specified instead
+  // Legacy field, ignored by Bazel.
   repeated DefaultCpuToolchain default_toolchain = 4;
 
   // All the toolchains in this release.