feat(nix/binify): add binify

Create a store path where the executable `exe` is linked to
$out/bin/${name}. This is useful for e.g. including it as a “package”
in `buildInputs` of a shell.nix.

For example, if I have the exeutable /nix/store/…-hello, I can make it
into /nix/store/…-binify-hello/bin/hello with
`binify { exe = …; name = "hello" }`.

Change-Id: I600bdcd8f143bca2dd8dfbb165a9a5a8d6397622
Reviewed-on: https://cl.tvl.fyi/c/depot/+/624
Reviewed-by: tazjin <mail@tazj.in>

nix/binify/default.nix

@@ -0,0 +1,16 @@
+{ pkgs, lib, ... }:
+
+# Create a store path where the executable `exe`
+# is linked to $out/bin/${name}.
+# This is useful for e.g. including it as a “package”
+# in `buildInputs` of a shell.nix.
+#
+# For example, if I have the exeutable /nix/store/…-hello,
+# I can make it into /nix/store/…-binify-hello/bin/hello
+# with `binify { exe = …; name = "hello" }`.
+{ exe, name }:
+
+pkgs.runCommandLocal "binify-${name}" {} ''
+  mkdir -p $out/bin
+  ln -sT ${lib.escapeShellArg exe} $out/bin/${lib.escapeShellArg name}
+''