* Compile with gcc5 to avoid the compiler bug described in
https://gcc.gnu.org/ml/gcc-patches/2014-05/msg02560.html
* Add a patch to fix the many incorrect printf format specifiers and
other sloppy type conversions that gcc5 catches and warns on
(erroring out due to -Werror).
Local build and run successful.
From the ChangeLog:
```
Version 0.7.77, 2015-09-02
+ #B941, MXF: files having only a video stream and an ancillary data
stream were having incorrect second video stream
+ MOV: detection of r210 CodecID as raw RGB
+ Ancillary data: detection of all metadata blocks (previously: only the
first one was detected)
x MPEG-TS: Wrong demux of TSP (188+16 TS) files having PES with only
padding x MediaTrace #2: XML malformed with Flags items (hotfix, flags
meaning disabled in XML output)
x MediaTrace #3: XML malformed with some MP4 files
x MediaTrace #6: XML duplicated attributes
x MediaTrace #10: versioned xsd, creating library name and version
x MediaTrace: XML content was not escaped
x #B947, Amazon S3 support (REST API v2), CLI/DLL only and if compiled
with libcurl support: Analyze file on s3 was not working if secret key
contains / character
```
Without this, users are presented with this endless loop:
$ ffplay
The program ‘ffplay’ is currently not installed. You can install it by
typing:
nix-env -i ffmpeg
$ nix-env -i ffmpeg
$ ffplay
The program ‘ffplay’ is currently not installed. You can install it by
typing:
nix-env -i ffmpeg
Fixes this problem, when building apps in QtCreator:
...(compile output window)
g++ -Wl,-rpath,/nix/store/1w7h7p6s2srfw2ady90k7072991lrnpp-qtbase-5.4.2/lib \
-o qt-test3 main.o mainwindow.o moc_mainwindow.o \
-L/nix/store/1w7h7p6s2srfw2ady90k7072991lrnpp-qtbase-5.4.2/lib \
-lQt5Widgets -lQt5Gui -lQt5Core -lGL -lpthread
/nix/store/b8qhjrwf8sf9ggkjxqqav7f1m6w83bh0-binutils-2.23.1/bin/ld: cannot find -lGL
collect2: error: ld returned 1 exit status
mesa is already in the closure of Qt, so there is no size increase.
The patch is copied into both qt-5.3 and qt-5.4 directories, like other
patches are.
Note that programs still can _run_ against a different libGL (e.g. one
provided by nvidia) by configuring the dynamic linker. For instance,
NixOS sets the LD_LIBRARY_PATH environment variable to
/run/opengl-driver/lib/, meaning that whatever libGL is found there
will be used instead of the default (mesa).
