qmake set arbitrary makefile variable from qmake

[33333]

Hi.

I want to set some arbitrary variable in the makefile generated by qmake. How can I do this? I can't imaging this can't be done but can't find mention of it anywhere.

Use case; I want to generate a makefile compatible with the GNU stds, which entails defining vars in the make file such as "prefix" that can be overridden when running the make file. So for example my .pro would look like:

TEMPLATE = app
TARGET = foo
CONFIG += ...
CCFLAGS += -g
prefix=/usr/local/
exec_prefix=$(prefix)
bindir=$(exec_prefix)/bin
datarootdir=$(prefix)/share
datadir=$(datarootdir)
libdir=$(exec_prefix)/lib
...

TEMPLATE = app
TARGET = foo
CONFIG += ...
CCFLAGS += -g
prefix=/usr/local/
exec_prefix=$(prefix)
bindir=$(exec_prefix)/bin
datarootdir=$(prefix)/share
datadir=$(datarootdir)
libdir=$(exec_prefix)/lib
...

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But I need most of those variables exported to the Makefile.

Thanks.