Try to fix failing build not finding java by pinning the version from…

… 23 to 21

build.sh

@@ -1,6 +1,32 @@
 #!/bin/sh
 # Build script for Netlify
 
-brew install openjdk # As of Nov 2023, Netlify still only has v8 :'(
+## Get newer Java
+## (1) Brew
+# Broken - somehow, the java binary is there but we can't execute it (bad user??)
+#brew install openjdk@21 # As of Nov 2024, Netlify still only has v8 :'(
+#export PATH="/home/linuxbrew/.linuxbrew/opt/openjdk@21/libexec/bin:$PATH"
+#echo "DBG: java version $(/home/linuxbrew/.linuxbrew/opt/openjdk@21/libexec/bin/java --version)"
+
+## (2) DIY; source: https://answers.netlify.com/t/java-11-support/67078/19
+CACHE_DIR=$NETLIFY_BUILD_BASE/cache
+JAVA_DOWNLOAD_URL="https://download.java.net/java/GA/jdk17.0.2/dfd4a8d0985749f896bed50d7138ee7f/8/GPL/openjdk-17.0.2_linux-x64_bin.tar.gz"
+JAVA_RELEASE=jdk-17.0.2 # Must match directory inside archive in JAVA_DOWNLOAD_URL
+currentver="$(java -version 2>&1 |head -n1 | cut -d'"' -f2 |cut -d'.' -f1)"
+requiredver="11" # Shadow-cljs requires a minimum of Java 11
+# Version check shamelessly copied from StackOverflow:
+# https://unix.stackexchange.com/a/285928
+if [ ! "$(printf '%s\n' "$requiredver" "$currentver" | sort -V | head -n1)" = "$requiredver" ]; then
+  echo "Java version 11 is required as minimum by Shadow-cljs (found Java version $currentver)"
+  if [ ! -d "$CACHE_DIR/$JAVA_RELEASE" ]; then
+    echo "Downloading $JAVA_RELEASE since it isn't available in cache"
+    wget --quiet -O openjdk.tar.gz $JAVA_DOWNLOAD_URL
+    tar xf openjdk.tar.gz --directory $CACHE_DIR
+  fi
+  echo "Enabling $JAVA_RELEASE from cache, by making it available on PATH"
+  export PATH=$CACHE_DIR/$JAVA_RELEASE/bin:$PATH
+fi
+
+# Build the site
 clojure -M:build
 npx -y pagefind --site public