Comment 3 for bug 1779539

Ah, nevermind. The "stdlib" option is ignored (it used to control macOS only).

* Is this vanilla Ubuntu 16.04 or Kubuntu/Xubuntu/Mint/etc.?

Building with:
scons stdlib=libc++ hss1394=0 mad=0 faad=0 ffmpeg=1 shoutcast=0 opus=0 vamp=0 coreaudio=0 hid=0 verbose=0 qt5=1 -j4
on Ubuntu 16.04.3 works for me.

What's confusing is, libQt5Network.so should be dynamically linked to libz.so, and so missing zlib symbols doesn't make much sense. Can you post the output from your system for each bullet below:

* Can you post the full build log from scons and your config.log file?
* What version of libQt5Network and libz do you have? Here's what I have:
$ dpkg --list zlib1g
ii zlib1g:amd64 1:1.2.8.dfsg-2ubuntu4.1
$ dpkg --list libqt5network
ii libqt5network5:amd64 5.5.1+dfsg-16ubuntu7.5
* Please past the output of this command:
$ ldd /usr/lib/x86_64-linux-gnu/libQt5Network.so
        linux-vdso.so.1 => (0x00007ffdb3ffc000)
        libQt5Core.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 (0x00007f6368810000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f63685f3000)
        libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f63683d9000)
        libproxy.so.1 => /usr/lib/x86_64-linux-gnu/libproxy.so.1 (0x00007f63681b8000)
        libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f6367e36000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f6367a6c000)
        libicui18n.so.55 => /usr/lib/x86_64-linux-gnu/libicui18n.so.55 (0x00007f636760a000)
        libicuuc.so.55 => /usr/lib/x86_64-linux-gnu/libicuuc.so.55 (0x00007f6367276000)
        libpcre16.so.3 => /usr/lib/x86_64-linux-gnu/libpcre16.so.3 (0x00007f6367010000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f6366e0c000)
        libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f6366afb000)
        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f63668f3000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f63665ea000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f63663d4000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f6368ce6000)
        libicudata.so.55 => /usr/lib/x86_64-linux-gnu/libicudata.so.55 (0x00007f636491d000)
        libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f63646ad000)

And if you could, please post:
$ objdump -T /lib/x86_64-linux-gnu/libz.so.1 | grep inflate
$ objdump -T /usr/lib/x86_64-linux-gnu/libQt5Network.so | grep inflate