Allow for heroku variant build.

- Create agent "flavor" flags (none, fips, heroku)
- These can be used from the command line to install different pieces of the agent as needed.
- Use the distinction to install the correct set of OSS licenses.
- Fix license file for libpopt

Changing for heroku will invalidate the cache, but I can live with that
- it is a smaller build than the rest, an already a distinct pipeline
- for now, we are only using it for the packaging layers.  My plan is to adopt project files to be able to limit the scope of the flavor flag so that it will not reach outside of //packages/...

This is a precursor to #44033 and #44183, which add top level package targets for the distinct distribution artifacts.
At that time, the "select()"ion of all deps will happen from the top, and we won't need license generation in //compliance.

Author: aiuto

compliance/BUILD.bazel

@@ -12,6 +12,19 @@ py_binary(
     deps = ["//tasks:licenses"],
 )
 
+filegroup(
+    name = "all_agent_deps",
+    srcs = [
+        "//deps:all_deps",
+    ] + select({
+        "//packages/agent:linux_heroku": [],
+        "//conditions:default": [
+            # This will become "//deps/openscap:all_deps" in the future
+            "@popt",
+        ],
+    }),
+)
+
 # Gather the licenses for dependencies that not built by omnibus any more.
 # The target is a temporary hack. In the future, it should become //distrib:agent.
 license_csv(
@@ -20,7 +33,7 @@ license_csv(
     licenses_dir = "licenses_dir",
     offers_dir = "sources_dir",
     tags = ["manual"],
-    target = "//deps:all_deps",
+    target = ":all_agent_deps",
 )
 
 # Turn the copied licenses into a target we can feed to other rules.
@@ -62,7 +75,7 @@ filter_directory(
     strip_prefix = ".",
 )
 
-# You would expect that filter_directory returns something usuable to pkg_* rules.
+# You would expect that filter_directory returns something usable to pkg_* rules.
 # It does not, so we have to wrap it.
 pkg_files(
     name = "offer_copies",

deps/BUILD.bazel

@@ -29,7 +29,6 @@ filegroup(
             "@libxslt",
             "@nghttp2",
             "@pcre2",
-            "@popt",
             "@zstd",
         ],
         "//:macos_arm64": [

omnibus/config/software/datadog-agent-finalize.rb

@@ -25,7 +25,9 @@
     # TODO too many things done here, should be split
     block do
         # Push all the pieces built with Bazel.
-        command_on_repo_root "bazelisk run -- //packages/install_dir:install --destdir=#{install_dir}",  env: {"BUILD_WORKSPACE_DIRECTORY" => "." }
+
+        # TODO: flavor can be defaulted and set from the bazel wrapper based on the environment.
+        command_on_repo_root "bazelisk run --//:install_dir=#{install_dir} --//packages/agent:flavor=#{flavor_arg} -- //packages/install_dir:install"
 
         # Conf files
         if windows_target?
@@ -64,6 +66,7 @@
             delete "#{install_dir}/embedded/include/dbus-1.0"
         end
 
+        # TODO: Rather than move these, let's install them to the right place to start
         if linux_target?
             # Move configuration files
             mkdir "#{output_config_dir}/etc/datadog-agent"

packages/agent/BUILD.bazel

@@ -0,0 +1,45 @@
+# Agent packages
+
+load("@bazel_skylib//lib:selects.bzl", "selects")
+load("@bazel_skylib//rules:common_settings.bzl", "string_flag")
+
+package(default_visibility = ["//visibility:public"])
+
+string_flag(
+    name = "flavor",
+    build_setting_default = "base",
+    # These values match omnibus.
+    values = [
+        "base",
+        "fips",
+        "heroku",
+    ],
+)
+
+alias(
+    name = "default_flavor",
+    actual = ":base_flavor",
+)
+
+config_setting(
+    name = "base_flavor",
+    flag_values = {"@@//packages/agent:flavor": "base"},
+)
+
+config_setting(
+    name = "fips_flavor",
+    flag_values = {"@@//packages/agent:flavor": "fips"},
+)
+
+config_setting(
+    name = "heroku_flavor",
+    flag_values = {"@@//packages/agent:flavor": "heroku"},
+)
+
+selects.config_setting_group(
+    name = "linux_heroku",
+    match_all = [
+        ":heroku_flavor",
+        "@platforms//os:linux",
+    ],
+)

packages/install_dir/BUILD.bazel

@@ -29,11 +29,27 @@ pkg_filegroup(
     }),
 )
 
+# All the things that belong in /etc
+# This is not strictly in install_dir but it is a cousin.
+# TODO: split this cleanly.  The way the omnibus script works
+# is to install everything into install_dir (/opt/datadog-agent)
+# and then bulk move things to {output_dir}/etc/ in the finalizer.
+# We need to fix that so we just generate to the right place. For
+# now, let's just try to keep etc things separate.
+pkg_filegroup(
+    name = "etc",
+    srcs = [
+        "//deps/snmp_traps:all_files",
+    ],
+)
+
+# Gather everything that goes in /opt/datadog-agent/...
 pkg_install(
     name = "install",
     srcs = [
         ":embedded",
+        ":etc",
         ":licenses",
-        "//deps/snmp_traps:all_files",
     ],
+    destdir_flag = "//:install_dir",
 )