Revert "Use the new component dependency option of the rust-toolchain file"

This reverts commit 648caced6e.

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scripts/cargo.sh

@@ -4,7 +4,7 @@ dir=$(dirname "$0")
 source "$dir/config.sh"
 
 # read nightly compiler from rust-toolchain file
-TOOLCHAIN=$(cat "$dir/rust-toolchain" | grep channel | sed "s/channel = \"\(.*\)\"/\1/")
+TOOLCHAIN=$(cat "$dir/rust-toolchain")
 
 cmd=$1
 shift || true

scripts/rustup.sh

@@ -8,7 +8,7 @@ case $1 in
 
         echo "=> Installing new nightly"
         rustup toolchain install --profile minimal "nightly-${TOOLCHAIN}" # Sanity check to see if the nightly exists
-        sed -i "s/\"nightly-.*\"/\"nightly-${TOOLCHAIN}\"/" rust-toolchain
+        echo "nightly-${TOOLCHAIN}" > rust-toolchain
         rustup component add rustfmt || true
 
         echo "=> Uninstalling all old nighlies"