Feature listing

[tueda]

Maybe it would be helpful to have a command-line option to show a verbose version display, similar to the feature list shown in vim --version.

For example, form -vv could print something like:

FORM 5.0.0-beta.1 (May 30 2025, v5.0.0-beta.1-168-ge1289ac)
+alarm           +float +pipe     -windows
+debugging       +gmp   +posix    +zlib
+externalchannel +mpfr  -pthreads +zstd
-flint           -mpi   +system

Then check.rb could scan this feature list and provide a method like feature?("flint"). This would simplify the problem in #644 (comment); one could simply use #require feature?("flint").