Find JDK 9 on Windows

Change-Id: I8854d0e7fb23602e5ca20309fc79890b4f31a70e
Reviewed-on: https://gerrit.libreoffice.org/47479Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

configure.ac

@@ -6562,6 +6562,15 @@ if test "$ENABLE_JAVA" != ""; then
             bitness=32
         fi
 
+        if test -z "$with_jdk_home"; then
+            dnl See <https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-EEED398E-AE37-4D12-
+            dnl AB10-49F82F720027> section "Windows Registry Key Changes":
+            reg_get_value "$bitness" "HKEY_LOCAL_MACHINE/SOFTWARE/JavaSoft/JDK/CurrentVersion"
+            if test -n "$regvalue"; then
+                ver=$regvalue
+                reg_get_value "$bitness" "HKEY_LOCAL_MACHINE/SOFTWARE/JavaSoft/JDK/$ver/JavaHome"
+                _jdk_home=$regvalue
+            fi
             if test -z "$with_jdk_home"; then
                 for ver in 1.8 1.7 1.6; do
                     reg_get_value "$bitness" "HKEY_LOCAL_MACHINE/SOFTWARE/JavaSoft/Java Development Kit/$ver/JavaHome"
@@ -6570,6 +6579,7 @@ if test "$ENABLE_JAVA" != ""; then
                         break
                     fi
                 done
+            fi
             if test -f "$_jdk_home/lib/jvm.lib" -a -f "$_jdk_home/bin/java.exe"; then
                 with_jdk_home="$_jdk_home"
                 howfound="found automatically"