You could write the qmake snippet below. In short, you would need to take a look at the following qmake variables:
PKGCONFIG
test.pro
TEMPLATE = app
TARGET = test
INCLUDEPATH += .
LIBS += -L /usr/local/lib -lsbml -lstdc++ -lm
unix {
CONFIG += link_pkgconfig
PKGCONFIG += libsbml
}
HEADERS += test.h
SOURCES += test.cpp