Introduce Bazel flag and config setting to disable copy_file_range

This allows changing this behavior from a dependent Bazel workspace much easier and will only invalidate the cache of this target (and dependencies) when changed.
In contrast setting `cops` globally would invalidate all cache.

PiperOrigin-RevId: 679644291

MODULE.bazel

@@ -13,6 +13,10 @@ bazel_dep(
     version = "2.1.0",
     repo_name = "absl_py",
 )
+bazel_dep(
+    name = "bazel_skylib",
+    version = "1.7.1",
+)
 bazel_dep(
     name = "boringssl",
     version = "0.0.0-20240530-2db0eb3",

riegeli/bytes/BUILD

@@ -1,10 +1,22 @@
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
+
 package(
     default_visibility = ["//visibility:public"],
     features = ["header_modules"],
 )
 
 licenses(["notice"])
 
+bool_flag(
+    name = "use_copy_file_range",
+    build_setting_default = True,
+)
+
+config_setting(
+    name = "disable_copy_file_range",
+    flag_values = {":use_copy_file_range": "False"},
+)
+
 cc_library(
     name = "reader",
     hdrs = ["reader.h"],
@@ -1074,6 +1086,10 @@ cc_library(
         "//conditions:default": ["fd_writer.h"],
     }),
     hdrs = ["fd_reader.h"],
+    defines = select({
+        "//riegeli/bytes:disable_copy_file_range": ["RIEGELI_DISABLE_COPY_FILE_RANGE"],
+        "//conditions:default": [],
+    }),
     # fd_reader.cc has #define before #include to influence what the included
     # files provide.
     features = ["-use_header_modules"],