Failing to build Firefox on NixOS

gistfile1.txt

> nix-shell ../nixpkgs-mozilla/release.nix -A gecko.x86_64-linux.gcc  --command fish --show-trace
these derivations will be built:
  /nix/store/v8inr2yp8x7248f22zcpnkds2dwdri2v-rust-cbindgen-0.8.6.drv
building '/nix/store/v8inr2yp8x7248f22zcpnkds2dwdri2v-rust-cbindgen-0.8.6.drv'...
unpacking sources
unpacking source archive /nix/store/m7i0f17szrdy8q56iyvbk9fcajx605ds-source
source root is source
unpacking source archive /nix/store/1gh299a9hy5kfcsgryxqlxinwbnz1gik-rust-cbindgen-0.8.6-vendor
patching sources
configuring
building
Running cargo build --release
error: failed to acquire package cache lock

Caused by:
  failed to open: /homeless-shelter/.cargo/.package-cache

Caused by:
  Permission denied (os error 13)
builder for '/nix/store/v8inr2yp8x7248f22zcpnkds2dwdri2v-rust-cbindgen-0.8.6.drv' failed with exit code 101
error: build of '/nix/store/v8inr2yp8x7248f22zcpnkds2dwdri2v-rust-cbindgen-0.8.6.drv' failed