this moves us another step towards the "outer" configure doing just
minimal bootstrapping of qmake.
a challenge here was that so far, qmake itself needed qconfig.cpp. this
was replaced by usage of a qt.conf file instead of compiled-in values.
however, to make the executable still self-contained, that qt.conf is
embedded into it (by simple appending of a fixed signature and the text
file).
the qmake with the embedded qt.conf is not used for the qt build itself,
which instead relies on the qt.conf in bin/ as before. however, due to
the missing built-in values, this file now needs to contain more
information than before. but except for a minimal version that is needed
to start up qmake/configure at all, that file is now also generated with
qmake. as some of the newly set up properties are subsequently used by
configure itself, qmake gains a (deliberately undocumented) function to
reload the qt.conf after it's fully populated.
unlike the old implementations, this one doesn't emit redundant qt.conf
entries which match the hard-coded fallbacks. omitting them leads to
leaner files which are more comprehensible.
Started-by: Paolo Angelelli <paolo.angelelli@qt.io>
Change-Id: I4526ef64b3c89d9851e10f83965fe479ed7f39f6
Reviewed-by: Jake Petroules <jake.petroules@qt.io>
169a40d511