Run the tests unconditionally and skip if the shaper is not available.
This fixes distcheck (https://github.com/harfbuzz/harfbuzz/pull/3504)
and shows SKIP for these tests instead of ignoring them.
We implicitly require it for building ragel subproject. This new version
requirement should satisfied in both Fedora 33 and Debian bullseye, and
not be too cutting edge for us.
No idea why test names are underscorified but it it just makes calling
meson test testname harder than it should being not able to copy file
name directly.
Khaled Hosny
Behdad Esfahbod