iOS: Remove need for -force_load of platform plugin

Instead of force-loading the whole static library of the platform plugin
we tell the linker to look for the missing symbol qt_registerPlatformPlugin.
This symbol is provided by the same object file as the plugin's static
initializer, so the object file is included in the final binary and
the static initializer is run, resulting in the plugin registering with
Qt.

We could have marked the actual static initializer wrapper provided by
Q_IMPORT_PLUGIN(QIOSIntegrationPlugin) as undefined, but due to the C++
mangling this would look less intuitive on the linker command line than
the custom dummy function that we provide, which has C linkage.

Change-Id: I6805537e1f49260a41d48c555376964cb1fe75d8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
iOS: Remove need for separate qtiosmain library

We can combine the hybrid and non-hybrid use-cases into a single static
library if we are careful about which symbols are included in which
object files. By limiting the main() and qt_user_main() functions to
their own translation units, the linker will only pick them up if they
are missing at link time (the user's program do not provide them).

This technique is resilient to the -ObjC linker flag, which includes all
object files that implement an ObjectiveC class or category, but will
fail if the -all_load flag is passed to the linker, as we'll then have
duplicate symbols for either main() or qt_user_main(). The latter should
not happen unless the user provides the flag manually, and in the case
he or she does, there's ways to work around it by providing less global
flags such as -ObjC or -force_load.

Change-Id: Ie2f8e10a7265d007bf45cb1dd83f19cff0693551
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
make stubs for dangerous/useless qmake functions in limited mode

sync up implementation with lupdate & creator. no actual effect on
qmake.

Change-Id: I1bdeb759e895e4200f09332dadf8a6cef348182f
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
(cherry picked from qttools/94ab2efb2d155d3c1ca7b91c1daf443a149bcf1f)
fetch all properties from qmake

sync up implementation with lupdate & creator. no actual effect on
qmake.

don't filter out ^QMAKE_.*:
- QMAKE_MKSPECS is not printed any more, so needs no filtering
- QMAKE_VERSION can be simply used now, as we are now rather close to the
  real qmake
- QMAKE_SPEC and QMAKE_XSPEC need to be fetched
  - this fixes the default spec resolution

Change-Id: Ifcfa8b5b9e2bbf5d995940e1bb7f55e7d67aed3e
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
(cherry picked from qttools/0037bef09ca77c5ae4d20bd09294ba1d57537e09)
add missing ifdefery

sync up implementation with qtcreator.

Change-Id: I6a1578818512fa3b0773faf276a1d56881eb06d7
(cherry picked from qttools/582cbddc6ba1b74a7e4e07e0b5c23d47de6838cb)
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
find features/ under mkspecs/ of source & build root

we were finding features/ directly in the source & build root, and we
were finding features/ under mkspecs/ from $QMAKEPATH and other mkspecs
locations, but we omitted the "transitive hull". this was
counterintuitive.

Change-Id: I9823e6606467c98f264c81385250da92311f51ca
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
make .qmake.{super,cache,conf} find "anchored" features

these files function as "anchors" for mkspecs/ and features/ directories
used by projects which load these files. ironically, these files didn't
see these feature files themselves.

Change-Id: I590855eb4a9d2c72b9abfcaa431d2f85a719c6e2
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
remove pointless string conversion

Change-Id: I1640083007ed0c428dfb8ab5ce8b68a7d7e2a749
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
introduce /src qmake property variants

this is for shadow builds during build time, where the respective files
are expected in the source dir.

Change-Id: I18dcfbdef99e1562a51dacac333642cae8105ebd
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
don't copy mkspecs to build directory

instead, teach qmake to use the mkspecs dir from the source dir as well.

Change-Id: I9edac11f8997fcb0594d0a67419d4733dd4ed86b
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
don't copy/symlink doc/global to build dir

instead, use the files directly from the source dir.

Change-Id: I03b728c66de6e03cade6dc153dcc78cea8e3f606
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>