these things probably have the same cause, i think - the build can have paths gc'd from under them

       > checking for riscv64-unknown-linux-gnu-gcc... riscv64-unknown-linux-gnu-gcc
       > checking whether the C compiler works... no
       > configure: error: in '/build/hello-2.12.3':
       > configure: error: C compiler cannot create executables
       > See 'config.log' for more details

terminating due to unexpected unrecoverable internal error: Assertion 'false' failed in nix::DerivationTrampolineGoal::init()::<lambda()> at ../src/libstore/build/derivation-trampoline-goal.cc:125

this one is probably the fetcher thing?

       … while calling the 'import' builtin
         at /home/dram/code/config/flake.nix:53:24:
           52|     flake-utils.lib.eachDefaultSystem (system: {
           53|       legacyPackages = import nixpkgs {
             |                        ^
           54|         inherit system;

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: path '/nix/store/yxn9vm8hjp9j9vkn1979bh9rzg2gga94-source' is not valid

here's another error from the gc process

finding garbage collector roots...
deleting garbage...
deleting '/nix/store/tmp-942181-1014327575'
1 store paths deleted, 0.0 KiB freed
error:
       … While deleting garbage in store directory "/home/dram/tmp/teststore/nix/store/tmp-942181-1014327575"

       error: opening directory "/home/dram/tmp/teststore/nix/store/tmp-942181-1014327575/x/pkgs/by-name/an/anime4k": No such file or directory