Autogenerate a vendor-build.prop for the current product

The autogenerated soong vendor.img will use the autogenerated soong
vendor-build.prop module. The autogenerated vendor-build.prop module is
missing support for `android-info.txt` which is an additional input as
--prop-files. Support for that will be added in a followup CL.

Test: verified that autogenerated vendor.img for aosp_cf_x86_64_phone
contains a build.prop file, and its contents are equivalent to kati
built vendor build.prop file

Bug: 375500423
Change-Id: I46b3c2e7cf44300820dcd2f7a9799ad11730691e
diff --git a/Android.bp b/Android.bp
index d0f97db..cbe1c7b 100644
--- a/Android.bp
+++ b/Android.bp
@@ -164,6 +164,7 @@
     name: "product_config",
     visibility: [
         "//build/make/target/product/generic",
+        "//build/soong/fsgen",
     ],
 }