Auto-detect required bash, sed, and JDK versions (#297)

* Only start Hadoop Yarn if using Java 11 or older, since it doesn't
  start using newer Java versions (definitely doesn't work with 17, but
  the change that broke it occurred somewhere between 11 and 17, and may
  depend on whether you're running it with experimental flags; I'm not
  certain of which change broke it, but this gets Uno working again for
  both 11 and 17)
* Stop making assumptions about sed version based on Darwin OS. The user
  could have installed GNU sed. Instead, check for GNU sed vs. BSD sed
  explicitly
* Stop making assumptions about bash version based on Darwin OS. The
  user could have installed a newer version of bash. Instead, check the
  bash version explicitly for the feature that requires 4.1 or later

bin/impl/load-env.sh

@@ -122,10 +122,12 @@ fi
 hash shasum 2>/dev/null || { echo >&2 "shasum must be installed & on PATH. Aborting."; exit 1; }
 hash sed 2>/dev/null || { echo >&2 "sed must be installed & on PATH. Aborting."; exit 1; }
 
-if [[ $OSTYPE =~ ^darwin ]]; then
-  export SED="sed -i .bak"
-else
+if sed --version >/dev/null 2>&1; then
+  # GNU sed supports --version and -i without a backup suffix parameter
   export SED="sed -i"
+else
+  # BSD sed requires backup suffix parameter with -i
+  export SED="sed -i .bak"
 fi
 
 # load-env.sh

bin/impl/run/hadoop.sh

@@ -27,7 +27,13 @@ trap 'echo "[ERROR] Error occurred at $BASH_SOURCE:$LINENO command: $BASH_COMMAN
 
 "$HADOOP_HOME"/bin/hdfs namenode -format
 "$HADOOP_HOME"/sbin/start-dfs.sh
-"$HADOOP_HOME"/sbin/start-yarn.sh
+# Yarn won't start on newer versions of Java
+jver=$("$JAVA_HOME"/bin/java -version 2>&1 | grep version | cut -f2 -d'"' | cut -f1 -d.)
+if [[ $jver -gt 11 ]]; then
+  echo "Skipping yarn because it doesn't start on Java $jver"
+else
+  "$HADOOP_HOME"/sbin/start-yarn.sh
+fi
 
 namenode_port=9870
 if [[ $HADOOP_VERSION =~ ^2\..*$ ]]; then

bin/impl/util.sh

@@ -111,7 +111,9 @@ function setup_component() {
 }
 
 function save_console_fd {
-  if [[ -z $UNO_CONSOLE_FD && ! $OSTYPE =~ ^darwin ]]; then
+  # this requires at least bash 4.1
+  local v=("${BASH_VERSINFO[@]}")
+  if [[ -z $UNO_CONSOLE_FD ]] && (( v[0]>4 || (v[0]==4 && v[1]>=1) )); then
     # Allocate an unused file descriptor and make it dup stdout
     # https://stackoverflow.com/a/41620630/7298689
     exec {UNO_CONSOLE_FD}>&1