[clang] [clang] Track function template instantiation from definition (PR #112241)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

This change breaks compiling Qt. To reproduce on e.g. Linux, clone https://github.com/qt/qtbase, check out the tag `v6.8.1`, configure and build it like this:
```
$ cmake .. \
        -G Ninja \
        -DCMAKE_C_COMPILER=clang \
        -DCMAKE_CXX_COMPILER=clang++ \
        -DCMAKE_BUILD_TYPE=Release \
        -DQT_BUILD_EXAMPLES=OFF \
        -DQT_BUILD_TESTS=OFF \
        -DINPUT_opengl=no
$ ninja src/gui/CMakeFiles/Gui.dir/kernel/qwindowsysteminterface.cpp.o
/home/martin/code/qtbase/src/gui/kernel/qwindowsysteminterface.cpp:102:73: error: cannot initialize a parameter of type 'QWindowSystemInterfacePrivate::WindowSystemEvent *' with an rvalue of type 'QWindowSystemInterface::SynchronousDelivery *' 
  102 |             if (!QWindowSystemInterfacePrivate::eventHandler->sendEvent(&event))
      |                                                                         ^~~~~~
[...]
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
```

Please revert (and don't backport this) until this is sorted out.

https://github.com/llvm/llvm-project/pull/112241