Remove remaining config_settings, now that they're unnecessary and us…

…e macOS system libs (#260)

* Remove Bazel workaround, crushing longer term TODO

Fix to bazelbuild/bazel#13047 landed in 5.1

* Use system zlib on macOS
Part of the macOS API as with all on all other Apple platforms

* Parallel to zlib, use system bz2 on Apple platforms.
Note that unlike libz, bz2 is not bundled with Android

* Add note about lzma being private API on Apple platforms

BUILD.bzip2

@@ -1,10 +1,21 @@
 # Description:
 #   bzip2 is a high-quality data compressor.
 
+load("@bazel_skylib//lib:selects.bzl", "selects")
+
 licenses(["notice"])  # BSD derivative
 
-cc_library(
+alias(
     name = "bz2lib",
+    visibility = ["//visibility:public"],
+    actual = selects.with_or({
+        ("@platforms//os:osx", "@platforms//os:ios", "@platforms//os:watchos", "@platforms//os:tvos"): ":bz2lib_system",
+        "//conditions:default": ":bz2lib_source",
+    })
+)
+
+cc_library(
+    name = "bz2lib_source",
     srcs = [
         "blocksort.c",
         "bzlib.c",
@@ -19,5 +30,10 @@ cc_library(
         "bzlib.h",
     ],
     includes = ["."],
-    visibility = ["//visibility:public"],
+)
+
+# For OSs that bundle bz2lib
+cc_library( 
+    name = "bz2lib_system",
+    linkopts = ["-lbz2"],
 )

BUILD.lzma

@@ -40,38 +40,14 @@ copy_file(
 alias(
     name = "apple_config",
     actual = select({
-        ":aarch64": "config.lzma-ios-arm64.h",
-        ":arm": "config.lzma-ios-armv7.h",
-        ":x86_64": "config.lzma-osx-x86_64.h", # Configuration same as macOS
-        ":x86_32": "config.lzma-ios-i386.h",
+        "@platforms//cpu:aarch64": "config.lzma-ios-arm64.h",
+        "@platforms//cpu:arm": "config.lzma-ios-armv7.h",
+        "@platforms//cpu:x86_64": "config.lzma-osx-x86_64.h", # Configuration same as macOS
+        "@platforms//cpu:x86_32": "config.lzma-ios-i386.h",
     }),
 )
 
-# Longer term TODO: Blocked until at least after Bazel 5.1 has been released.
-# config_setting()s wrappers for constraint_values are necessary for alias rules in Bazel because of a bug in 5.0
-# Needs release of fix to https://github.com/bazelbuild/bazel/issues/13047, which will likely happen in 5.1
-# At that time, remove these config settings below and update their use in the alias above to the raw @platforms//os constraint_value()s
-# Note: There are other instances of this message to update or resolve in sync.
-
-config_setting(
-    name = "aarch64",
-    constraint_values = ["@platforms//cpu:aarch64"],
-)
-
-config_setting(
-    name = "arm",
-    constraint_values = ["@platforms//cpu:arm"],
-)
-
-config_setting(
-    name = "x86_64",
-    constraint_values = ["@platforms//cpu:x86_64"],
-)
-
-config_setting(
-    name = "x86_32",
-    constraint_values = ["@platforms//cpu:x86_32"],
-)
+# Note: lzma is bundled with Apple platforms, but sadly, not considered public API because its header is not exposed. lzma is not bundled on Android.
 
 cc_library(
     name = "lzma",

BUILD.zlib

@@ -6,45 +6,11 @@ alias(
     name = "zlib",
     visibility = ["//visibility:public"],
     actual = selects.with_or({
-        (":android", ":ios", ":watchos", ":tvos"): ":zlib_system",
+        ("@platforms//os:android", "@platforms//os:osx", "@platforms//os:ios", "@platforms//os:watchos", "@platforms//os:tvos"): ":zlib_system",
         "//conditions:default": ":zlib_source",
     })
 )
 
-# Longer term TODO: Blocked until at least after Bazel 5.1 has been released.
-# config_setting()s wrappers for constraint_values are necessary for alias rules in Bazel because of a bug in 5.0
-# Needs release of fix to https://github.com/bazelbuild/bazel/issues/13047, which will likely happen in 5.1
-# At that time, remove these config settings below and update their use in the alias above to the raw @platforms//os constraint_value()s
-# Note: There are other instances of this message to update or resolve in sync.
-
-config_setting(
-    name = "android",
-    constraint_values = [
-        "@platforms//os:android",
-    ],
-)
-
-config_setting(
-    name = "ios",
-    constraint_values = [
-        "@platforms//os:ios",
-    ],
-)
-
-config_setting(
-    name = "watchos",
-    constraint_values = [
-        "@platforms//os:watchos",
-    ],
-)
-
-config_setting(
-    name = "tvos",
-    constraint_values = [
-        "@platforms//os:tvos",
-    ],
-)
-
 cc_library(
     name = "zlib_source",
     srcs = [