build: Add --disable-java option to configure (bug #37838). * configure.ac: Use AC_ARG_ENABLE macro to add --disable-java option. Use AC_ARG_VAR to grab JAVA_HOME value from environment if it exists. Set Automake Conditional AMCOND_HAVE_JAVA if Java Interface is being built. * libinterp/dldfcn/__java__.cc: Include <config.h> and wrap file in #ifdef HAVE_JAVA. * scripts/Makefile.am: Use AMCOND_HAVE_JAVA to control building of Java interface.

--- a/libinterp/dldfcn/__java__.cc
+++ b/libinterp/dldfcn/__java__.cc
@@ -14,6 +14,11 @@
 ** along with this program; If not, see <http://www.gnu.org/licenses/>.
 */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#ifdef HAVE_JAVA
 #include "__java__.h"
 
 #include "parse.h"
@@ -2037,3 +2042,6 @@
     }
   return retval;
 }
+
+#endif
+