[roll] Roll fuchsia [build][sdk] Test generate_prebuild_idk.py

The `validation_data/` directory is based on the tree at commit
ccaf8865ac55a29a76a93426e6cde1f6da783bd9 [1]. `test_collection.json` is
a subset of the generated `sdk/prebuild/fuchsia_collection.json`. Each
atom type except Fuchsia packages is included once along with some
dependencies.

The `expected_idk/` is populated from the Ninja output for
`fuchsia_collection`(or `fuchsia_idk` due to differences described in
https://fxbug.dev/408003238).

[1] The "debug_libs" key for sysroot/meta.json was manually modified to
account for https://fxrev.dev/1246824.

Original-Bug: 338009514
Test: fx build //build/sdk/generate_prebuild_idk:generate_prebuild_idk_integration_test
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1246984
Original-Revision: c8b991c1d365f7321594e3bb84e761585712e20b
GitOrigin-RevId: d0347afe331d92b6bdaea140d494434f7d24f0c5
Change-Id: I79a613771538b21ee27d0b308ea0fcab7b82264a
diff --git a/stem b/stem
index f4eeafa..613f0eb 100644
--- a/stem
+++ b/stem
@@ -8,7 +8,7 @@
              root=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="cb08447574f25c3d3997313470e268214f585cfb"
+             revision="c8b991c1d365f7321594e3bb84e761585712e20b"
              />
   </imports>
 </manifest>