Addressed here: https://codereview.qt-project.org/c/qt/qtgrpc/+/488623 backported to 6.5 lts.

Thank you all ! It worked !!!!!

Yes the solution was TEMPLATE = lib !

qmake provides functions for processing the contents of variables during the configuration process.

As QMAKE_FILE_NAME is a run-time and not a configuration-time variable it cannot be edited by clean_path, seems this problem cannot be solved this way, anyone any ideas?

EDIT:

I think I finally found a proper solution:

PROTOS = interface_definitions.proto PROTOPATH = $$relative_path($$PWD, $$OUT_PWD) \

protoc is now being called this way:

protoc --cpp_out=. --proto_path=. --proto_path=../project/ ../project/interface_definitions.proto

everything works fine now!

Hi and welcome to the devnet,

I use protobuf too (in Windows, Linux and OSX).
In our OSX environment we build protobuf with

$PROTOBUF_SRC_DIR/configure --silent --prefix=$PREFIX --disable-shared --enable-dependency-tracking=no