您发布的链接对此进行了很好的解释.

Link you've posted explains that very well.

extralib.target = extra
extralib.commands = echo "Building extralib.."; \    # Run your programs here
                make -w -C ../my_libraries/extralib; \
                echo "Done building extralib."; \

extralib.depends =
QMAKE_EXTRA_TARGETS += extralib
PRE_TARGETDEPS = extra

因此，可以将其重写为

    extralib.target = extra
    extralib.commands = echo "Setuping the envirovment.."; \
                            export MYVAR="/usr/src/whatever" \
                            export SECONDVAR="/home/user" \
                            ./runScript.sh

    extralib.depends =



    QMAKE_EXTRA_TARGETS += extralib
    PRE_TARGETDEPS = extra