Error with clang18 in igraph

[krlmlr]

flang-new: error: unknown argument '-fvisibility=hidden'; did you mean '-Xclang -fvisibility=hidden'?

https://github.com/igraph/rigraph/actions/runs/9341386885/job/25708087211#step:6:75

Haven't looked closer.

[gaborcsardi]

If I follow that suggestion I get

flang-new-18 -Xclang -fvisibility=hidden -fpic  -O2 -pedantic -c vendor/arpack/dgetv0.f -o vendor/arpack/dgetv0.o
flang-new: error: unknown argument '-Xclang'; did you mean '-Xflang'?
flang-new: error: unknown argument '-fvisibility=hidden'; did you mean '-Xclang -fvisibility=hidden'?

The problem is that R was build with a Fortran compiler that supports -fvisibility=hidden, but then we use flang-new-18 to install packages, which does not. AFAICT there is no way to use -fvisibility=hidden with flang-new-18 now, so I'll remove that flag via our local Makevars.

[gaborcsardi]

Should be good tomorrow (Wednesday).