build-rust-crate: quote build script output env var

pkgs/build-support/rust/build-rust-crate/configure-crate.nix

@@ -224,7 +224,7 @@ in ''
 
      CRATENAME=$(echo ${crateName} | sed -e "s/\(.*\)-sys$/\U\1/" -e "s/-/_/g")
      grep -P "^cargo:(?!(rustc-|warning=|rerun-if-changed=|rerun-if-env-changed))" target/build/${crateName}.opt \
-       | awk -F= "/^cargo:/ { sub(/^cargo:/, \"\", \$1); gsub(/-/, \"_\", \$1); print \"export \" toupper(\"DEP_$(echo $CRATENAME)_\" \$1) \"=\" \$2 }" > target/env
+       | awk -F= "/^cargo:/ { sub(/^cargo:/, \"\", \$1); gsub(/-/, \"_\", \$1); print \"export \" toupper(\"DEP_$(echo $CRATENAME)_\" \$1) \"=\" \"\\\"\"\$2\"\\\"\" }" > target/env
      set -e
   fi
   runHook postConfigure