maint: Move to /rust/* to /

This makes it easier for tooling to find the Rust stuff.
Rust/non-rust is not a useful distinction in this repo anymore anyway.

rust/bindgen-gcc.sh

@@ -1,18 +0,0 @@
-
-# Rust bindgen uses Clang to generate bindings, but that means that it can't
-# find the "system" or compiler headers when the stdenv compiler is GCC.
-# This script tells it where to find them.
-
-echo "Extending BINDGEN_EXTRA_CLANG_ARGS with system include paths..." 2>&1
-BINDGEN_EXTRA_CLANG_ARGS="${BINDGEN_EXTRA_CLANG_ARGS:-}"
-export BINDGEN_EXTRA_CLANG_ARGS
-include_paths=$(
-  echo | $NIX_CC_UNWRAPPED -v -E -x c - 2>&1 \
-  | awk '/#include <...> search starts here:/{flag=1;next} \
-        /End of search list./{flag=0} \
-        flag==1 {print $1}'
-)
-for path in $include_paths; do
-  echo " - $path" 2>&1
-  BINDGEN_EXTRA_CLANG_ARGS="$BINDGEN_EXTRA_CLANG_ARGS -I$path"
-done