Rust example fails to compile on macOS because of libiconv

[YorikSar]

Describe the bug
When I try to build Rust example, I get a link error:

...
ERROR: /Users/tweag/workspaces/bazel_on_macos/rules_nixpkgs/examples/toolchains/rust/BUILD:3:12: Compiling Rust bin hello (1 files) failed: (Exit 1): process_wrapper failed: error executing command bazel-out/darwin-opt-exec-FFB32019/bin/external/rules_rust/util/process_wrapper/process_wrapper --subst 'pwd=${pwd}' -- external/nix_rust/bin/rustc hello.rs '--crate-name=hello' '--crate-type=bin' ... (remaining 16 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
error: linking with `external/local_config_cc/cc_wrapper.sh` failed: exit status: 1
  |
  = note: "external/local_config_cc/cc_wrapper.sh" "-m64" "-arch" "x86_64" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.0.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.1.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.2.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.3.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.4.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.5.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.6.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.7.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.8.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.hello.996e1e6f-cgu.9.rcgu.o" "bazel-out/darwin-fastbuild/bin/hello.2qbjdfrzgcayd1in.rcgu.o" "-L" "external/nix_rust/lib/rustlib/x86_64-apple-darwin/lib" "-L" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libstd-d43b1180a7c500d2.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libpanic_unwind-ae539223d447dfc6.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libobject-11a458d9b32a239c.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libmemchr-34cc6ee434399709.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libaddr2line-e4ce48db41321be4.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libgimli-925f8e621e87c5d1.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libstd_detect-f98ef5df1f347ad0.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/librustc_demangle-8ede71df0f2d7c4f.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libhashbrown-0a273c8fcff748a9.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_alloc-12eb4f87886f4dd7.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libunwind-93f5cbe2b90daf72.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libcfg_if-8032011eb1f3eb82.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/liblibc-22466d52281abdf1.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/liballoc-69c5dbacefc7f8b1.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_core-de984f3632fc3c42.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libcore-ec0cd9f6516ee01f.rlib" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib/libcompiler_builtins-eefc3cdb499abe56.rlib" "-lSystem" "-lresolv" "-lc" "-lm" "-liconv" "-L" "/nix/store/2dhyhzx18w0kqb1qq3h4wp1a0ng9dr3q-rustc-1.56.1/lib/rustlib/x86_64-apple-darwin/lib" "-o" "bazel-out/darwin-fastbuild/bin/hello" "-Wl,-dead_strip" "-nodefaultlibs" "-undefined" "dynamic_lookup" "-headerpad_max_install_names" "-lstdc++" "-lm"
  = note: ld: library not found for -liconv
          clang-7: error: linker command failed with exit code 1 (use -v to see invocation)
          

error: aborting due to previous error
...

To Reproduce

cd examples/toolchains/rust
nix-shell --command "bazel run --config=nix :hello"

Expected behavior
"Hello, world!" line should be written to the output.

Environment

• OS name + version: macOS Monterey 12.2.1 (also reproducible on CI with macos-11 builder
• Version of the code: Got this issue while trying to make examples work on macOS on this commit

[YorikSar]

It seems I can reproduce this without rules_nixpkgs: https://gist.github.com/YorikSar/d1cfc806b611c4506d2a1957c05653b7 - if I provide libiconv in the shell environment, rules_rust can't see it while plain rustc does.

[fricklerhandwerk]

Can reproduce.