/usr/include/gpgme++/ is in libgpgmepp-dev 1.8.0-3+b2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gpgme++/configuration.h
/usr/include/gpgme++/context.h
/usr/include/gpgme++/data.h
/usr/include/gpgme++/decryptionresult.h
/usr/include/gpgme++/defaultassuantransaction.h
/usr/include/gpgme++/editinteractor.h
/usr/include/gpgme++/encryptionresult.h
/usr/include/gpgme++/engineinfo.h
/usr/include/gpgme++/error.h
/usr/include/gpgme++/eventloopinteractor.h
/usr/include/gpgme++/exception.h
/usr/include/gpgme++/global.h
/usr/include/gpgme++/gpgadduserideditinteractor.h
/usr/include/gpgme++/gpgagentgetinfoassuantransaction.h
/usr/include/gpgme++/gpgmefw.h
/usr/include/gpgme++/gpgmepp_export.h
/usr/include/gpgme++/gpgmepp_version.h
/usr/include/gpgme++/gpgsetexpirytimeeditinteractor.h
/usr/include/gpgme++/gpgsetownertrusteditinteractor.h
/usr/include/gpgme++/gpgsignkeyeditinteractor.h
/usr/include/gpgme++/importresult.h
/usr/include/gpgme++/interfaces/
/usr/include/gpgme++/interfaces/assuantransaction.h
/usr/include/gpgme++/interfaces/dataprovider.h
/usr/include/gpgme++/interfaces/passphraseprovider.h
/usr/include/gpgme++/interfaces/progressprovider.h
/usr/include/gpgme++/key.h
/usr/include/gpgme++/keygenerationresult.h
/usr/include/gpgme++/keylistresult.h
/usr/include/gpgme++/notation.h
/usr/include/gpgme++/result.h
/usr/include/gpgme++/scdgetinfoassuantransaction.h
/usr/include/gpgme++/signingresult.h
/usr/include/gpgme++/swdbresult.h
/usr/include/gpgme++/tofuinfo.h
/usr/include/gpgme++/trustitem.h
/usr/include/gpgme++/verificationresult.h
/usr/include/gpgme++/vfsmountresult.h