select-java: query java version using -XshowSettings

instead of parsing the output of `-version`, parse output of
`-XshowSettings:properties`, whose format is more predicable.
as on EL9, we have

> Picked up JAVA_TOOL_OPTIONS: openjdk version "11.0.19" 2023-04-18 LTS OpenJDK Runtime Environment (Red_Hat-11.0.19.0.7-1.el9_1) (build 11.0.19+7-LTS) OpenJDK 64-Bit Server VM (Red_Hat-11.0.19.0.7-1.el9_1) (build 11.0.19+7-LTS, mixed mode, sharing)

while on fedora 38, jre-1.8 prints

> openjdk version "1.8.0_362"

jre-11 prints

> openjdk version "11.0.19" 2023-04-18

before this change, we just use `"` as the field separator for awk,
this works, but the parsing algorithm is fragile. so let's use the
"java.specification.version" property instead, it is always printed
like

>     java.specification.version = 1.8

so, after this change, we split this line with " = ", and pick the
last field, i.e., the value of `java.specification.version`.
also, in this change, we are using the case clause for better readability.

Fixes scylladb#212
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

scripts/select-java

@@ -26,10 +26,18 @@ function select_java_fedora() {
 }
 
 function select_java_others() {
-    javaver=$(/usr/bin/java -version 2>&1|head -n1|cut -f 3 -d " ")
-    if [[ "$javaver" =~ ^\"1.8.0 || "$javaver" =~ ^\"11.0. ]]; then
-        echo /usr/bin/java
-    fi
+    local java
+    local javaver
+    java=$1
+    shift
+    javaver=$($java -XshowSettings:properties -version 2>&1 | awk -F' = ' '/java.specification.version/ {print $NF}')
+    case "$javaver" in
+    1.8|11)
+        echo $java
+        ;;
+    *)
+        ;;
+    esac
 }
 
 . /etc/os-release
@@ -52,7 +60,7 @@ done
 if [ -n "$java" ]; then
     : # good
 elif [ -x /usr/bin/java ]; then
-    java=$(select_java_others)
+    java=$(select_java_others /usr/bin/java)
 fi
 if [ -z "$java" ]; then
     exit 1