Switch to a toolchain

Author: fmeum

src/conditions/BUILD.tools

@@ -145,11 +145,13 @@ config_setting(
 
 config_setting(
     name = "host_windows_x64_constraint",
+    deprecation = "No longer used by Bazel and will be removed in the future. Migrate to toolchains or define your own version of this setting.",
     values = {"host_cpu": "x64_windows"},
 )
 
 config_setting(
     name = "host_windows_arm64_constraint",
+    deprecation = "No longer used by Bazel and will be removed in the future. Migrate to toolchains or define your own version of this setting.",
     values = {"host_cpu": "arm64_windows"},
 )
 
@@ -159,6 +161,7 @@ alias(
         ":host_windows_arm64_constraint": ":host_windows_arm64_constraint",
         "//conditions:default": ":host_windows_x64_constraint",
     }),
+    deprecation = "No longer used by Bazel and will be removed in the future. Migrate to toolchains or define your own version of this setting.",
     visibility = ["//visibility:public"],
 )
 

tools/build_defs.bzl

@@ -114,4 +114,3 @@ def _make_current_toolchain_rule(toolchain_type):
     )
 
 current_launcher_binary = _make_current_toolchain_rule("//tools/launcher:launcher_toolchain_type")
-current_launcher_maker_binary = _make_current_toolchain_rule("//tools/launcher:launcher_maker_toolchain_type")

tools/launcher/BUILD.tools

@@ -3,30 +3,38 @@ load(
     "//tools:build_defs.bzl",
     "IS_HOST_WINDOWS",
     "current_launcher_binary",
-    "current_launcher_maker_binary",
     "single_binary_toolchain",
 )
 
 package(default_visibility = ["//visibility:public"])
 
-current_launcher_binary(name = "launcher")
-
-current_launcher_maker_binary(name = "launcher_maker")
+# WARNING: These targets and toolchain types only exist for the purposes of
+# rulesets formerly included in Bazel itself and may change or be removed at any
+# time.
 
-# WARNING: These toolchain types and their associated toolchains only exist for
-# the purposes of rulesets formerly included in Bazel itself and may change or
-# be removed at any time.
+current_launcher_binary(name = "launcher")
 
-toolchain_type(
-    name = "launcher_toolchain_type",
-    visibility = ["//visibility:private"],
+# DEPRECATED: Use the `:launcher_maker_toolchain_type` toolchain instead to
+# avoid an unnecessary dependency on a C++ toolchain when building for a
+# non-Windows platform.
+filegroup(
+    name = "launcher_maker",
+    srcs = select({
+        ":is_host": ["launcher_maker.exe" if IS_HOST_WINDOWS else "//src/tools/launcher:launcher_maker"],
+        "//conditions:default": ["//src/tools/launcher:launcher_maker"],
+    }),
 )
 
-toolchain_type(
-    name = "launcher_maker_toolchain_type",
+config_setting(
+    name = "is_host",
+    constraint_values = HOST_CONSTRAINTS,
     visibility = ["//visibility:private"],
 )
 
+toolchain_type(name = "launcher_toolchain_type")
+
+toolchain_type(name = "launcher_maker_toolchain_type")
+
 # Toolchains are prefixed with a number to ensure that their order of definition
 # matches their precedence in the toolchain resolution process when registered
 # with a wildcard pattern (which sorts by name).