Not sure what you worry about - the build looks perfectly fine ?

The warnings about "QtDesigner/QDesignerCustomWidgetInterface" being deprecated indicates, that Qwt uses an include path, that is going to be changed in a future version of Qt. As long as we don't have this version this not important and if it happens some day there will be an update of Qwt, with a version depending include path.

"Nothing to be done for `first'.", means, that there is nothing to do in a directory for a specific make target ( here "first" ) - also nothing wrong with it. F.e. in the doc directory there is no build rule ( as there is nothing to build ), but there is an install rules, when calling "make install"

Uwe