Undefined reference error with mingw compiler and mvsc compiled library - c++

Question

An undefined reference error on minGW 8.1 in Qt 5.15.2 with any build-up in VS2015. With mvsc 2015 and 2017, the compiler works fine, but with minGW, it gives an error on undefined reference. What needs to be done to make it work on minGW too? Has anyone come across this?
.pro file:
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
CONFIG += c++11
PRODDIR = "../.."
SOURCES += "$${PRODDIR}/include/qsecureblackbox.cpp" main.cpp archivewriter.cpp certificate.cpp filetablemodel.cpp newarchive.cpp openarchive.cpp progress.cpp
HEADERS += "$${PRODDIR}/include/qarchivereader.h" "$${PRODDIR}/include/qarchivewriter.h" "$${PRODDIR}/include/qasicsigner.h" "$${PRODDIR}/include/qasicverifier.h" "$${PRODDIR}/include/qauthenticator.h" "$${PRODDIR}/include/qauthenticodesigner.h" "$${PRODDIR}/include/qauthenticodeverifier.h" "$${PRODDIR}/include/qcadessigner.h" "$${PRODDIR}/include/qcadesverifier.h" "$${PRODDIR}/include/qcertificatemanager.h" "$${PRODDIR}/include/qcertificatestorage.h" "$${PRODDIR}/include/qcertificatevalidator.h" "$${PRODDIR}/include/qcrlmanager.h" "$${PRODDIR}/include/qcryptokeymanager.h" "$${PRODDIR}/include/qcryptokeystorage.h" "$${PRODDIR}/include/qdcauth.h" "$${PRODDIR}/include/qdcauthwebserver.h" "$${PRODDIR}/include/qdtlsclient.h" "$${PRODDIR}/include/qdtlsserver.h" "$${PRODDIR}/include/qftpclient.h" "$${PRODDIR}/include/qftpserver.h" "$${PRODDIR}/include/qhashfunction.h" "$${PRODDIR}/include/qhttpclient.h" "$${PRODDIR}/include/qhttpserver.h" "$${PRODDIR}/include/qimapclient.h" "$${PRODDIR}/include/qkmipclient.h" "$${PRODDIR}/include/qkmipserver.h" "$${PRODDIR}/include/qmailreader.h" "$${PRODDIR}/include/qmailwriter.h" "$${PRODDIR}/include/qmessagecompressor.h" "$${PRODDIR}/include/qmessagedecompressor.h" "$${PRODDIR}/include/qmessagedecryptor.h" "$${PRODDIR}/include/qmessageencryptor.h" "$${PRODDIR}/include/qmessagesigner.h" "$${PRODDIR}/include/qmessagetimestamper.h" "$${PRODDIR}/include/qmessagetimestampverifier.h" "$${PRODDIR}/include/qmessageverifier.h" "$${PRODDIR}/include/qoauthclient.h" "$${PRODDIR}/include/qocspmanager.h" "$${PRODDIR}/include/qocspserver.h" "$${PRODDIR}/include/qofficedecryptor.h" "$${PRODDIR}/include/qofficeencryptor.h" "$${PRODDIR}/include/qofficequicksigner.h" "$${PRODDIR}/include/qofficesigner.h" "$${PRODDIR}/include/qofficeverifier.h" "$${PRODDIR}/include/qotpclient.h" "$${PRODDIR}/include/qotpserver.h" "$${PRODDIR}/include/qpasswordvault.h" "$${PRODDIR}/include/qpdfdecryptor.h" "$${PRODDIR}/include/qpdfencryptor.h" "$${PRODDIR}/include/qpdfsigner.h" "$${PRODDIR}/include/qpdfverifier.h" "$${PRODDIR}/include/qpgpkeymanager.h" "$${PRODDIR}/include/qpgpkeyring.h" "$${PRODDIR}/include/qpgpreader.h" "$${PRODDIR}/include/qpgpwriter.h" "$${PRODDIR}/include/qpop3client.h" "$${PRODDIR}/include/qpublickeycrypto.h" "$${PRODDIR}/include/qrestclient.h" "$${PRODDIR}/include/qrestserver.h" "$${PRODDIR}/include/qrnd.h" "$${PRODDIR}/include/qsamlidpserver.h" "$${PRODDIR}/include/qsamlreader.h" "$${PRODDIR}/include/qsamlspserver.h" "$${PRODDIR}/include/qsamlwriter.h" "$${PRODDIR}/include/qsftpclient.h" "$${PRODDIR}/include/qsftpserver.h" "$${PRODDIR}/include/qsmtpclient.h" "$${PRODDIR}/include/qsoapclient.h" "$${PRODDIR}/include/qsoapquicksigner.h" "$${PRODDIR}/include/qsoapsigner.h" "$${PRODDIR}/include/qsoapverifier.h" "$${PRODDIR}/include/qsshclient.h" "$${PRODDIR}/include/qsshkeymanager.h" "$${PRODDIR}/include/qsymmetriccrypto.h" "$${PRODDIR}/include/qtlsclient.h" "$${PRODDIR}/include/qtlsserver.h" "$${PRODDIR}/include/qtspserver.h" "$${PRODDIR}/include/qusermanager.h" "$${PRODDIR}/include/qwebdavclient.h" "$${PRODDIR}/include/qwebdavserver.h" "$${PRODDIR}/include/qwebsocketclient.h" "$${PRODDIR}/include/qwebsocketserver.h" "$${PRODDIR}/include/qxadessigner.h" "$${PRODDIR}/include/qxadesverifier.h" "$${PRODDIR}/include/qxmldecryptor.h" "$${PRODDIR}/include/qxmlencryptor.h" "$${PRODDIR}/include/qxmlsigner.h" "$${PRODDIR}/include/qxmlverifier.h" archivewriter.h certificate.h filetablemodel.h newarchive.h openarchive.h progress.h
FORMS += archivewriter.ui certificate.ui newarchive.ui openarchive.ui progress.ui
INCLUDEPATH += "$${PRODDIR}/include"
DEPENDPATH += "$${PRODDIR}/include"
greaterThan(QT_MAJOR_VERSION, 4) { TARGET_ARCH = $${QT_ARCH} } else { TARGET_ARCH = $${QMAKE_HOST.arch} }
contains(TARGET_ARCH, x86_64) { LIBDIR = lib64 } else { LIBDIR = lib }
CONFIG(debug, debug|release) { VARIANT = debug } else { VARIANT = release }
PLATDIR = windows
LIBS += -ladvapi32
LIBNAME = qtsecureblackbox20
# Ensures the product's DLL is copied to the output directory.
LIBPATH = "$${PRODDIR}/$${LIBDIR}/$${PLATDIR}/$${LIBNAME}.dll"
copydll.commands = $(COPY_FILE) \"$$replace(LIBPATH, /, \\)\" \"$$replace(OUT_PWD, /, \\)\\$${VARIANT}\"
first.depends = $(first) copydll
export(first.depends)
export(copydll.commands)
QMAKE_EXTRA_TARGETS += first copydll
LIBS += -L"$${PRODDIR}/$${LIBDIR}/$${PLATDIR}" -l$${LIBNAME}