Clang crashes on -CURRENT while compiling port

[Fernando Apesteguía]

One of my ports (cad/openvsp) fails to compile in -CURRENT. The port
only compiles with gcc on < 12. As part of the debugging I changed to
compile with clang.

The compiler crashed while compiling the port with the following error:

fatal error: error in backend: No open frame
c++: error: clang frontend command failed with exit code 70

Compiler version is:

freebsd clang version 5.0.0 (brances/release_50 309439)

I can send the as_callfunc* upon request.

How to reproduce:

Change compiler:gcc-c++11-lib to compiler:c++14-lang in port's Makefile

Change src/external/glfont2/CMakeLists.txt and add /usr/local/include
(for some reason clang doesn't find GL/gl.h while gcc does...)

I can open a PR if necessary.

Cheers

P.S: I don't know if this belongs to freebsd-hackers@ since it is
related to -CURRENT or if it belongs to freebsd-ports@