only set SELINUX_ENABLED=1 on Linux

[sylvestre]

Fails on Mac otherwise with:

   Compiling crossterm v0.25.0
error: couldn't read /Users/sylvestre/dev/debian/coreutils/target/release/build/fts-sys-5da7dc1e06092d06/out/fts-sys.rs: No such file or directory (os error 2)
  --> /Users/sylvestre/.cargo/registry/src/index.crates.io-6f17d22bba15001f/fts-sys-0.2.2/src/lib.rs:30:1
   |
30 | include!(concat!(env!("OUT_DIR"), "/fts-sys.rs"));
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `include` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `fts-sys` (lib) due to previous error

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/timeout

[cakebaker]

Any idea why the ShellScript/Format task gets skipped with a "file not found" error?

[sylvestre]

dunno, sorry