[bootstrap]: fix stage1 build on nixos and improve download robustness

[lolbinarycat]

sorry for not formatting this as a PR, but i'm in the middle of drafting another PR, and i don't think i can split this into its own branch without making that pr unmergable.

this fixes an error where building stage1 on nixos would produce a rustc binary that is dynamically linked to libstdc++, but this dependency does not get patched, so the executable cannot be run without using LD_LIBRARY_PATH hacks.

diff --git a/src/bootstrap/src/core/download.rs b/src/bootstrap/src/core/download.rs
index a7f4bb0cf..2fa47cc6c 100644
--- a/src/bootstrap/src/core/download.rs
+++ b/src/bootstrap/src/core/download.rs
@@ -154,6 +154,7 @@ fn fix_bin_or_dylib(&self, fname: &Path) {
                     zlib
                     patchelf
                     stdenv.cc.bintools
+                    stdenv.cc.cc.lib
                 ];
             }
             ";
@@ -224,6 +225,7 @@ fn download_http_with_retries(&self, tempfile: &Path, url: &str, help_on_error:
             tempfile.to_str().unwrap(),
             "--retry",
             "3",
+            "--retry-all-errors",
             "-SRf",
         ]);
         // Don't print progress in CI; the \r wrapping looks bad and downloads don't take long enough for progress to be useful.

[lolbinarycat]

hmm, it seems like LD_LIBRARY_PATH=build/.nix-deps/lib is still required to run stage1, so i guess it's not a complete fix..?

[lolbinarycat]

cp build/.nix-deps/lib/libstdc++.so.6 build/x86_64-unknown-linux-gnu/stage1/lib/ seems to be required? should that be in the build scripts somewhere? idk it all seems very broken..

[tgross35]

Could you submit this as a PR please so it can be reviewed? If you don't want to disrupt your local branch/state, GitHub lets you edit the file on your fork directly (open the file and click the pencil icon).

Also as mentioned in #127616, it would be great if you could drop by on Zulip so it's a bit easier to get to the bottom of the problems and figure out how to fix them.

[lolbinarycat]

the actual fix seems to be related to this.