Add new goal for compat file generator

To generate compat files, we need the following files.

- base_plat_sepolicy: to get all types
- base_plat_pub_policy.cil: to get public types
- {ver}_plat_sepolicy: to get old types

This creates a new dist goal, base-sepolicy-files-for-mapping, to
conveniently generate and gather desired files under out/dist.

Bug: 214336258
Test: build/soong/soong_ui.bash --make-mode dist \
      base-sepolicy-files-for-mapping \
      TARGET_PRODUCT=aosp_arm64 TARGET_BUILD_VARIANT=userdebug
Change-Id: I2f210ab47be777cd91346d635f75064845821144
diff --git a/Android.bp b/Android.bp
index df1e264..0ca82a6 100644
--- a/Android.bp
+++ b/Android.bp
@@ -865,6 +865,9 @@
         "sepolicy_neverallows",
         "sepolicy_neverallows_vendor",
     ],
+    dist: {
+        targets: ["base-sepolicy-files-for-mapping"],
+    },
 }
 
 // policy for recovery
@@ -933,6 +936,9 @@
     name: "base_plat_sepolicy",
     srcs: [":base_plat_sepolicy.cil"],
     installable: false,
+    dist: {
+        targets: ["base-sepolicy-files-for-mapping"],
+    },
 }
 
 se_policy_conf {
@@ -1003,6 +1009,9 @@
     filter_out: [":reqd_policy_mask.cil"],
     secilc_check: false,
     installable: false,
+    dist: {
+        targets: ["base-sepolicy-files-for-mapping"],
+    },
 }
 
 se_policy_conf {