hooks/install: Make failure to find download location non-fatal

Sometimes builds fail because it can't find package download location.
It is a flaky issue but damages the stability of our builds.
Since download location is not required by the EO, it would be
better to make the failure non-fatal.

BUG=b/280086674
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I0765b38048d24197a2ce10ca0b3ab3172490de37
Reviewed-on: https://cos-review.googlesource.com/c/third_party/platform/crosutils/+/48589
Reviewed-by: Dexter Rivera <riverade@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>

hooks/install/gen-sbom-package-info.py

diff --git a/hooks/install/gen-sbom-package-info.py b/hooks/install/gen-sbom-package-info.py
index 38948dd..989197f 100755
--- a/hooks/install/gen-sbom-package-info.py
+++ b/hooks/install/gen-sbom-package-info.py
@@ -26,6 +26,7 @@
 
 
 SBOM_INFO_FILE_NAME = "sbom-pkg-info.json"
+SPDX_NOASSERTION = "NOASSERTION"
 
 
 class SbomPackageInfo:
@@ -110,8 +111,10 @@
         ) = licenses.get_licenses(build_info_dir, src_path, package_name)
         sbom_pkg_info.go_dep = go_dep.get_go_dep(src_path)
 
+        # Since download location is not required by the EO, failure to
+        # find download location shouldn't be fatal.
         if not sbom_pkg_info.download_url and not sbom_pkg_info.private:
-            raise SBOMPkgInfoError(f"download url not found")
+            sbom_pkg_info.download_url = SPDX_NOASSERTION
         if not sbom_pkg_info.licenses:
             sbom_pkg_info.licenses = "NONE"
     except Exception as e: