Add quote on the command output

The quote is necessary for shell in CI environment.

Bug: 426097289
Test: build/soong/tests/sbom_test.sh
Test: go/abtd/run/L98900030014291262
Change-Id: Id5bc94cc5297874d7ac0ace71c3ce6fbcc86031a
diff --git a/tests/sbom_test.sh b/tests/sbom_test.sh
index f2b255a..4dce313 100755
--- a/tests/sbom_test.sh
+++ b/tests/sbom_test.sh
@@ -340,7 +340,7 @@
         echo "Checksum is wrong: ${apex_file}#${filename}"
         diff_found=true
       fi
-    done <<< $(grep -E '("fileName":)|("checksumValue":)'  ${apex_file}.spdx.json | sed -E 's/(.*"fileName": |.*"checksumValue": )"(.*)",?/\2/')
+    done <<< "$(grep -E '("fileName":)|("checksumValue":)'  ${apex_file}.spdx.json | sed -E 's/(.*"fileName": |.*"checksumValue": )"(.*)",?/\2/')"
   done
   if [ $diff_found = "true" ]; then
     echo "Diff found, exit with error."