os: add NixOS to the constraint values
NixOS uses the Linux kernel, but that's where commonality with the
myriad Linux distributions out there stops. Like the different BSD's,
NixOS is sufficiently different that it warrants a constraint value.
In particular, no non-static binary has any chance of running on NixOS
unless it was specifically built for it, because the dynamic linker is
in a non-standard location. This means that toolchains downloaded as
part of host autoconfiguration that detect Linux (like
`go_register_toolchains()`) always fail on NixOS.
NixOS is a popular operating system used by thousands, one of the most
active projects on all of GitHub, and with more unique packages than
even Debian, Fedora or Gentoo according to https://repology.org/.
diff --git a/os/BUILD b/os/BUILD
index 16df5d3..16525d3 100644
--- a/os/BUILD
+++ b/os/BUILD
@@ -76,3 +76,11 @@
name = "qnx",
constraint_setting = ":os",
)
+
+# NixOS uses the Linux kernel, but is not ABI-compatible with any
+# other Linux distribution. This is because the dynamic linker is in
+# a non-standard (and undefined) location on the filesystem.
+constraint_value(
+ name = "nixos",
+ constraint_setting = ":os",
+)
