Remove readarray from install.sh (#1198)

## Summary

This isn't available on macOS (see, e.g.,
https://stackoverflow.com/questions/23842261/alternative-to-readarray-because-it-does-not-work-on-mac-os-x),
but this version works both on macOS and Linux.

Closes https://github.com/astral-sh/puffin/issues/1196. (Verified
locally and on CI.)

scripts/bootstrap/install.sh

@@ -80,7 +80,10 @@ link_executables() {
 }
 
 # Read requested versions into an array
-readarray -t versions < "$versions_file"
+versions=()
+while IFS= read -r version; do
+    versions+=("$version")
+done < "$versions_file"
 
 # Install each version
 for version in "${versions[@]}"; do
@@ -95,7 +98,6 @@ for version in "${versions[@]}"; do
         continue
     fi
 
-
     url=$(jq --arg key "$key" '.[$key] | .url' -r < "$versions_metadata")
 
     if [ "$url" == 'null' ]; then