make install on macOS failing at strip command for non library targets

I have cross platform project. This project has INSTALL targets which does not only install the build products (libraries and applications) but also a series of external libraries and also the Qt5 libraries/plugins via custom INSTALLS targets. One example how the Qt5 bearer plugins are installed:

macx: qt5_bearer_plugins_target.files *= $$[QT_INSTALL_PLUGINS]/bearer/*.dylib
qt5_bearer_plugins_target.path = $${PREFIX}/bin/bearer
INSTALLS += qt5_bearer_plugins_target

Prefix is just the installation root. However, for all those targets, a strip command is called but without arguments from QMAKE_STRIPFLAGS_LIB. This results in the following error:

strip /Users/roland/projects/vatsim/build-swift-Desktop_Qt_5_9_0_clang_64bit-Debug/dist/bin/bearer/libqgenericbearer.dylib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/strip: symbols referenced by indirect symbol table entries that can't be stripped in: /Users/roland/projects/vatsim/build-swift-Desktop_Qt_5_9_0_clang_64bit-Debug/dist/bin/bearer/libqgenericbearer.dylib

Question is whether qmake should detect that this is a library and append QMAKE_STRIPFLAGS_LIB or should custom targets ever be stripped?