rust: 1.17.0 -> 1.20.0

simplify the boostrap hashes a bit

build with bundled llvm:

the rust project has forked the llvm compiler to solve some
issues.
With pkgs.llvm the test suite fails.

See https://github.com/rust-lang/rust/pull/43026

And PR #30088

pkgs/development/compilers/rust/print-hashes.sh

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+set -euo pipefail
 
 # All rust-related downloads can be found at
 # https://static.rust-lang.org/dist/index.html.  To find the date on
@@ -6,25 +7,30 @@
 # file, e.g.
 # https://static.rust-lang.org/dist/channel-rust-beta-date.txt
 
-PLATFORMS="i686-unknown-linux-gnu x86_64-unknown-linux-gnu i686-apple-darwin x86_64-apple-darwin"
-BASEURL="https://static.rust-lang.org/dist"
-DATE=$1
-VERSION=$2
+PLATFORMS=(
+  i686-unknown-linux-gnu
+  x86_64-unknown-linux-gnu
+  i686-apple-darwin
+  x86_64-apple-darwin
+)
+BASEURL=https://static.rust-lang.org/dist
+VERSION=${1:-}
+DATE=${2:-}
 
-if [[ -z  $DATE ]]
-then
-    echo "No date supplied"
-    exit -1
-fi
-
-if [[ -z  $VERSION ]]
+if [[ -z $VERSION ]]
 then
     echo "No version supplied"
     exit -1
 fi
 
-for PLATFORM in $PLATFORMS
+if [[ -n $DATE ]]
+then
+    BASEURL=$BASEURL/$DATE
+fi
+
+for PLATFORM in "${PLATFORMS[@]}"
 do
-    URL="$BASEURL/$DATE/rust-$VERSION-$PLATFORM.tar.gz.sha256"
-    curl $URL
+    URL="$BASEURL/rust-$VERSION-$PLATFORM.tar.gz.sha256"
+    SHA256=$(curl -sSfL $URL | cut -d ' ' -f 1)
+    echo "$PLATFORM = \"$SHA256\";"
 done