[antlir2][packager] create separate build appliance for packaging use cases

Summary:
This diff creates a separate build appliance for packaging rules that is independent of the target image OS.

Changes:
1. Created a new `packager-appliance` layer and rule in `//antlir/antlir2/antlir2_packager/facebook/` that includes the `build-appliance-features` for packaging
2. Added `msdk.builder` for the packager-appliance for better performance
3. Updated the package rules attrs to use this new packager-appliance as the default `build_appliance` for packaging operations (internally)
4. Created `default_attrs_base` in attrs.bzl to separate attrs that don't include the packager-specific build_appliance
5. Updated `unprivileged_dir` to use `default_attrs_base` combined with `attrs_selected_by_cfg` (OS-specific build appliance) since it needs to build dot_meta layers
6. Removed the packager `build-appliance-features` from the layer build appliance features since packaging now uses its own appliance

This allows packaging to be done with a consistent build appliance regardless of the target image OS, while still allowing users to customize it if needed.

[Session trajectory link](https://www.internalfb.com/intern/devai/devmate/inspector/?id=a5c24bee-ebf3-45f5-a42c-adb356739e9e)

Test Plan:
Built the packager-appliance successfully:
```
buck2 build fbcode//antlir/antlir2/antlir2_packager/facebook:packager-appliance
```

Ran package tests that passed:
```
buck2 test fbcode//antlir/antlir2/test_images/package/unprivileged_dir/...
buck2 test fbcode//antlir/antlir2/test_images/package/tar/...
buck2 test fbcode//antlir/antlir2/test_images/package/cpio/...
buck2 test fbcode//antlir/antlir2/test_images/package/ext3/...
buck2 test fbcode//antlir/antlir2/test_images/package/ext4/...
buck2 test fbcode//antlir/antlir2/test_images/package/rpm/...
```

(Some sendstream tests fail due to infrastructure issues with BTRFS ioctl permissions in Sandcastle, not related to these changes)

Reviewed By: justintrudell

Differential Revision: D94938828

fbshipit-source-id: e36dd3fbadc75f46f3d17dfbc8306c5cf8ced949

Author: vmagro

antlir/antlir2/antlir2_packager/BUCK

@@ -1,4 +1,7 @@
 load("//antlir/antlir2/bzl/feature:defs.bzl", "feature")
+load("//antlir/antlir2/bzl/image:defs.bzl", "image")
+load("//antlir/antlir2/bzl/package:defs.bzl", "package")
+load("//antlir/antlir2/facebook/images/build_appliance:defs.bzl", "build_appliance_from_dir")
 load("//antlir/bzl:build_defs.bzl", "rust_binary")
 load("//antlir/bzl:internal_external.bzl", "internal_external")
 
@@ -77,7 +80,7 @@ feature.new(
         }),
         ":btrfs-progs",
     ],
-    visibility = ["//antlir/antlir2/build_appliance/..."],
+    visibility = [],
 )
 
 feature.new(
@@ -101,3 +104,25 @@ feature.new(
     ),
     visibility = [],
 )
+
+image.layer(
+    name = "packager-appliance.layer",
+    default_os = "centos9",
+    features = [
+        ":build-appliance-features",
+    ],
+    visibility = [],
+)
+
+package.unprivileged_dir(
+    name = "packager-appliance.dir",
+    default_os = "centos9",
+    layer = ":packager-appliance.layer",
+    visibility = ["//antlir/antlir2/antlir2_packager/facebook/..."],
+)
+
+build_appliance_from_dir(
+    name = "packager-appliance",
+    dir = ":packager-appliance.dir",
+    visibility = ["PUBLIC"],
+)

antlir/antlir2/build_appliance/BUCK

@@ -33,7 +33,6 @@ feature.new(
             subdirs_to_create = "out",
         ),
         "//antlir/antlir2/package_managers/dnf/build_appliance:features",
-        "//antlir/antlir2/antlir2_packager:build-appliance-features",
     ],
     visibility = [
         "PUBLIC",

antlir/antlir2/bzl/package/attrs.bzl

@@ -4,6 +4,7 @@
 # LICENSE file in the root directory of this source tree.
 
 load("//antlir/antlir2/bzl:platform.bzl", "arch_select")
+load("//antlir/antlir2/bzl:types.bzl", "BuildApplianceInfo")
 load("//antlir/antlir2/bzl/image:cfg.bzl", "attrs_selected_by_cfg")
 load("//antlir/antlir2/features:defs.bzl", "FeaturePluginInfo", "FeaturePluginPluginKind")
 load(":cfg.bzl", "layer_attrs")
@@ -19,8 +20,8 @@ common_attrs = {
     ),
 } | layer_attrs
 
-# Attrs that are not expected for users to pass
-default_attrs = {
+# Base attrs that are not expected for users to pass (without build_appliance)
+default_attrs_base = {
     "_analyze_feature": attrs.exec_dep(default = "antlir//antlir/antlir2/antlir2_depgraph_if:analyze"),
     "_antlir2": attrs.exec_dep(default = "antlir//antlir/antlir2/antlir2:antlir2"),
     "_antlir2_packager": attrs.default_only(attrs.exec_dep(default = "antlir//antlir/antlir2/antlir2_packager:antlir2-packager")),
@@ -29,4 +30,13 @@ default_attrs = {
     "_target_arch": attrs.default_only(attrs.string(
         default = arch_select(aarch64 = "aarch64", x86_64 = "x86_64"),
     )),
-} | attrs_selected_by_cfg
+} | {k: v for k, v in attrs_selected_by_cfg.items() if k != "build_appliance"}
+
+# Attrs that are not expected for users to pass (includes packager build_appliance)
+default_attrs = default_attrs_base | {
+    "build_appliance": attrs.exec_dep(
+        providers = [BuildApplianceInfo],
+        default = "antlir//antlir/antlir2/antlir2_packager:packager-appliance",
+        doc = "Build appliance for packaging. Defaults to a standard packager-appliance that is independent of the target image OS.",
+    ),
+}

antlir/antlir2/bzl/package/unprivileged_dir.bzl

@@ -7,7 +7,7 @@ load("//antlir/antlir2/bzl:types.bzl", "LayerInfo")
 load("//antlir/antlir2/bzl/image:cfg.bzl", "attrs_selected_by_cfg")
 load("//antlir/antlir2/features:defs.bzl", "FeaturePluginPluginKind")
 load("//antlir/buck2/bzl:ensure_single_output.bzl", "ensure_single_output")
-load(":attrs.bzl", "common_attrs", "default_attrs")
+load(":attrs.bzl", "common_attrs", "default_attrs_base")
 load(":cfg.bzl", "package_cfg")
 load(":macro.bzl", "package_macro")
 load(":stamp_buildinfo.bzl", "stamp_buildinfo_rule")
@@ -83,7 +83,7 @@ _unprivileged_dir = rule(
     impl = _unprivileged_dir_impl,
     cfg = package_cfg,
     uses_plugins = [FeaturePluginPluginKind],
-    attrs = default_attrs | common_attrs | _unprivileged_dir_attrs,
+    attrs = default_attrs_base | common_attrs | _unprivileged_dir_attrs | attrs_selected_by_cfg,
 )
 
 unprivileged_dir_anon = anon_rule(
@@ -92,7 +92,7 @@ unprivileged_dir_anon = anon_rule(
         "base64_encoded_path_mapping": lambda x: ensure_single_output(x[DefaultInfo].sub_targets["base64_encoded_path_mapping"]),
         "package": lambda x: ensure_single_output(x),
     },
-    attrs = default_attrs | common_attrs | _unprivileged_dir_attrs,
+    attrs = default_attrs_base | common_attrs | _unprivileged_dir_attrs | attrs_selected_by_cfg,
 )
 
 unprivileged_dir = package_macro(_unprivileged_dir)