ffc.h: Remove clang ifdefs

[kolemannix]

Testing if this works; I compiled locally with gcc and it worked.

cmake -B build \
  -DCMAKE_C_COMPILER=gcc \
  -DCMAKE_CXX_COMPILER=g++ \
  -DCMAKE_BUILD_TYPE=Release
...

[lemire]

Running tests. Looking good so far.

[kolemannix]

GCC success! I think the msvc fails are just the VLA issue again; the latest main should not have that problem. Will CMake pull from github fresh on every run?

[lemire]

I will pull out my trusty Windows laptop.

Will CMake pull from github fresh on every run?

Well. There is no disk buffer anywhere. It has no choice to load it up fresh from the network.

[lemire]

I will merge and review Visual Studio separately.