Fix qt5, taglib, and c++ compiler detection
commit ac4182a9:
meson: Revamp qt5qml plugin and example build code
Stricter and simpler. For example, now we properly error out when
gstreamer-gl-1.0 was not found when the qt5 plugin is enabled or when
a C++ compiler is not enabled.
Note: view this patch with 'ignore whitespace'; it's mostly re-indentation.
commit 90fff266:
meson: Fix gstgl checks for qt and gtk
Also rename from build_ to have_, which is more accurate.
commit 33e4e081:
meson: Make C++ compiler detection not be automagic
It is now controlled by the qt5 and/or taglib options. We won't
silently fail to build taglib now.