Sure, but that's not the hard bit. The toolchains that I've seen so far all generate code for a static set of RISC-V extensions and that set of extensions become the target platform's identity. Sort of like we've seen variations like 'armhf+gnueabi' before, except with RISC-V several of these 'extensions' are pretty much mandatory to get performance parity. The resolution of these ISA extensions is much higher than other architectures. That's part of the appeal, for sure. You can design a Just Right RISC-V without wasting any power or area supporting features you don't need.
But until or unless the extensions stabilize to a canonical popular set (maybe this has already happened, or is happening soon), I wonder if the extension soup will cause some to be hesitant to adopt.
Whatever hesitancy I am imagining is not holding back some super swift progress on all kinds of awesome RISC-V stuff.
When you configure RISC-V gcc you tell it what default set of extensions you want it to use, but you can always tell it a different set with -march. I think that can't even be disabled.
It may be that the toolchains you've seen were built with only one set of libraries. If you specify --enable-multilib when you build the toolchain then libraries for a dozen or so common combinations of extensions are built.
If you're doing something embedded then you can build precisely the core and toolchain you want. If you're doing an OS for packaged software then you'll specify one (or a very small number) of combinations of extensions. Linux distributions such as Debian and Fedora decided on RV64GC a few years ago already.
By the end of this year the B and V extensions (and a few smaller ones) should be ratified and the Linux distros will make a second set of supported extensions.
But until or unless the extensions stabilize to a canonical popular set (maybe this has already happened, or is happening soon), I wonder if the extension soup will cause some to be hesitant to adopt.
Whatever hesitancy I am imagining is not holding back some super swift progress on all kinds of awesome RISC-V stuff.