Allow /usr/grte to exist in EdgeOS builds

BUG=b/290986313
TEST=Built a VM image with this and didn't get shot down by hook script
RELEASE_NOTE=None

Change-Id: I90cf0e8b8e5cebcdd4bec5a50186a546ded1b228
Reviewed-on: https://cos-review.googlesource.com/c/third_party/platform/crosutils/+/61862
Reviewed-by: Alan Berryhill <berryhill@google.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>

hooks/filesystem-layout.py

diff --git a/hooks/filesystem-layout.py b/hooks/filesystem-layout.py
index c57e5d2..111cd15 100755
--- a/hooks/filesystem-layout.py
+++ b/hooks/filesystem-layout.py
@@ -88,6 +88,10 @@
 # Paths that are allowed in the /usr dir for the SDK chroot.
 VALID_HOST_USR = set()
 
+VALID_EDGEOS_USR = {
+    "grte",
+}
+
 # Paths under /usr that should not have any subdirs.
 NOSUBDIRS_USR = {
     "bin",
@@ -191,7 +195,7 @@
     return False
 
 
-def check_usr(usr, host=False):
+def check_usr(usr, host=False, edgeos=False):
     """Check the /usr filesystem at |usr|."""
     ret = True
 
@@ -217,6 +221,9 @@
             logging.warning("Ignoring known bad /usr install for now")
             unknown -= {"www"}
 
+    if edgeos:
+        unknown -= VALID_EDGEOS_USR
+
     if unknown:
         logging.error(
             "Paths are not allowed in the /usr dir: %s", sorted(unknown)
@@ -303,7 +310,7 @@
                 "Package has improved; please update BAD_RUN_PACKAGES"
             )
 
-    if not check_usr(os.path.join(root, "usr"), host):
+    if not check_usr(os.path.join(root, "usr"), host, edgeos):
         ret = False
 
     return ret