[roll] Roll fuchsia [gigaboot] Add a gbl-installer image

Builds a dedicated gbl-installer image. This is done for two reasons.

1. We'll initially only use GBL for installer and continue to use
   gigaboot for normal boot. Thus both images are needed.
2. One issue of using GBL fastboot for NUC bootstrap is that users have
   to have serial connection and open a console and press `f` to enter
   fastboot. For headless installer flow, we want to avoid this
   dependency. The dedicated installer image can be configured to always
   stop in fastboot first, so users can just plugin the USB, reboot and
   they should always be able to bootstrap regardless of the current
   state of the device.

Original-Bug: 282797139

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1160337
Original-Revision: 5f2bbfb5c9a91f0063d510d319887bada1dc839d
GitOrigin-RevId: 5b54d682bd96bc4e743f2f00e71cab2deec14401
Change-Id: If700421c4ce1adda4bd9d25e093ee6626d95f7bc
diff --git a/stem b/stem
index 03cc1b6..9c2897f 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="e58fe4cd8cf738aa85de8e6fc5563d439b32475a"/>
+             revision="5f2bbfb5c9a91f0063d510d319887bada1dc839d"/>
   </projects>
   <hooks>
     <hook name="install-environment"