/usr/include/gcr-3/gcr/ is in libgcr-3-dev 3.18.0-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gcr-3/gcr/gcr-base.h
/usr/include/gcr-3/gcr/gcr-certificate-chain.h
/usr/include/gcr-3/gcr/gcr-certificate-request.h
/usr/include/gcr-3/gcr/gcr-certificate.h
/usr/include/gcr-3/gcr/gcr-collection.h
/usr/include/gcr-3/gcr/gcr-column.h
/usr/include/gcr-3/gcr/gcr-comparable.h
/usr/include/gcr-3/gcr/gcr-deprecated-base.h
/usr/include/gcr-3/gcr/gcr-enum-types-base.h
/usr/include/gcr-3/gcr/gcr-filter-collection.h
/usr/include/gcr-3/gcr/gcr-fingerprint.h
/usr/include/gcr-3/gcr/gcr-icons.h
/usr/include/gcr-3/gcr/gcr-import-interaction.h
/usr/include/gcr-3/gcr/gcr-importer.h
/usr/include/gcr-3/gcr/gcr-library.h
/usr/include/gcr-3/gcr/gcr-mock-prompter.h
/usr/include/gcr-3/gcr/gcr-parser.h
/usr/include/gcr-3/gcr/gcr-pkcs11-certificate.h
/usr/include/gcr-3/gcr/gcr-prompt.h
/usr/include/gcr-3/gcr/gcr-secret-exchange.h
/usr/include/gcr-3/gcr/gcr-secure-memory.h
/usr/include/gcr-3/gcr/gcr-simple-certificate.h
/usr/include/gcr-3/gcr/gcr-simple-collection.h
/usr/include/gcr-3/gcr/gcr-system-prompt.h
/usr/include/gcr-3/gcr/gcr-system-prompter.h
/usr/include/gcr-3/gcr/gcr-trust.h
/usr/include/gcr-3/gcr/gcr-types.h
/usr/include/gcr-3/gcr/gcr-union-collection.h
/usr/include/gcr-3/gcr/gcr-unlock-options.h
/usr/include/gcr-3/gcr/gcr-version.h
/usr/include/gcr-3/gcr/gcr.h