[PATCH nixpkgs] stdenv: update aarch64 musl bootstrap tools

[Alyssa Ross <hi@alyssa.is>]

This will allow removing some workarounds (661dfd83478 and the
preceding commits) that I had to do to get aarch64 musl to bootstrap,
and hopefully will also fix some of the bootstrapping failures we've
been seeing since then on newer aarch64 hardware.

This approach unfortunately requires users to have the Spectrum binary
cache set up, but it's the best we can do for now.  When it's
stabilized, we could use builtins.fetchClosure, which would avoid that
requirement.  But hopefully by that point we can have the bootstrap
tools updated upstream anyway.

Signed-off-by: Alyssa Ross <hi@alyssa.is>
---
 .../linux/bootstrap-files/aarch64-musl.nix       | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/pkgs/stdenv/linux/bootstrap-files/aarch64-musl.nix b/pkgs/stdenv/linux/bootstrap-files/aarch64-musl.nix
index 252783cce47..64c950529e9 100644
--- a/pkgs/stdenv/linux/bootstrap-files/aarch64-musl.nix
+++ b/pkgs/stdenv/linux/bootstrap-files/aarch64-musl.nix
@@ -1,11 +1,9 @@
+let
+  # This path is available on the Spectrum binary cache.
+  # See <https://spectrum-os.org/doc/binary-cache.html>.
+  build = builtins.storePath /nix/store/bq9z1m3dvcsk522j9li43gm61caj5ybr-stdenv-bootstrap-tools-aarch64-unknown-linux-musl;
+in
 {
-  busybox = import <nix/fetchurl.nix> {
-    url = "https://wdtz.org/files/wjzsj9cmdkc70f78yh072483x8656nci-stdenv-bootstrap-tools-aarch64-unknown-linux-musl/on-server/busybox";
-    sha256 = "01s6bwq84wyrjh3rdsgxni9gkzp7ss8rghg0cmp8zd87l79y8y4g";
-    executable = true;
-  };
-  bootstrapTools = import <nix/fetchurl.nix> {
-    url = "https://wdtz.org/files/wjzsj9cmdkc70f78yh072483x8656nci-stdenv-bootstrap-tools-aarch64-unknown-linux-musl/on-server/bootstrap-tools.tar.xz";
-    sha256 = "0pbqrw9z4ifkijpfpx15l2dzi00rq8c5zg9ghimz5qgr5dx7f7cl";
-  };
+  busybox = "${build}/on-server/busybox";
+  bootstrapTools = "${build}/on-server/bootstrap-tools.tar.xz";
 }
-- 
2.35.1