This commit fixes an issue caused by a new behavior in Qt 5.4.1 that
causes
PWD to be included in the default INCLUDEPATH on Windows with the nmake/VS
generators.
This new behavior was implemented in the following Qt commit:
qtbase/a90bb5b89a - centralize/unify/sanitize INCLUDEPATH "enrichment")
a90bb5b89a
This is a problem because our codecs in 3rdparty use two distinct
config.h files: one for Win32, and one for everything else.
The Win32 variant lives in the Win32 subdirectory of the build root.
The build root is the directory that will be added automatically by
the new Qt behavior. Typically, the build root has a build suffix,
for example 'speex-build'.
The regular config.h - the one for everything else but Win32 - lives
in the buildroot itself.
This new Qt behavior caused the wrong config.h file to be included
on Windows. Since the build root is now in the INCLUDEPATH,
the config.h file that lives in the build root now takes precedence
over the one in the Win32 directory.
To restore the old behavior for the codec builds, we use Qt config
option called 'no_include_pwd'. That explicitly tells qmake to not
include the PWD in the INCLUDEPATH. This restores the previous
behavior on Windows.
The 'no_include_pwd' config option has been around in Qt for a while.
It was not introduced with the aforementioned change to Qt, so it
doesn't break backwards compatibility for us.
d855b67d10