Add check if Java is >= 8

With Java >= 8 instead of javah, it is preferred to use javac
with option -h. In later Java versions, javah is removed.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

acinclude.m4.in

@@ -5766,9 +5766,12 @@ if test "x$kde_java_bindir" != "xno"; then
     if test ! -x "$kde_java_bindir/javac"; then
       AC_MSG_ERROR([javac not found under $kde_java_bindir - it seems you passed a wrong --with-java.])
     fi
+    kde_javac_h=`$kde_java_bindir/javac -h 2>&1 | grep "invalid flag"`
+    if test -n "$kde_javac_h"; then
       if test ! -x "$kde_java_bindir/javah"; then
         AC_MSG_ERROR([javah not found under $kde_java_bindir. javac was found though! Use --with-java or --without-java.])
       fi
+    fi
     if test ! -x "$kde_java_bindir/jar"; then
       AC_MSG_ERROR([jar not found under $kde_java_bindir. javac was found though! Use --with-java or --without-java.])
     fi
@@ -5875,7 +5878,23 @@ else
   AC_MSG_RESULT([none found])
 fi
 
+AC_MSG_CHECKING([if Java is >= 8])
+JAVA8=false
+if test -x "$kde_java_bindir/javac"; then
+  kde_javac_h=`$kde_java_bindir/javac -h 2>&1 | grep "invalid flag"`
+  if test -z "$kde_javac_h"; then
+    JAVA8=true
+    JAVAH=
+  fi
+fi
+if $JAVA8; then
+  AC_MSG_RESULT(yes)
+else
+  AC_MSG_RESULT(no)
+fi
+
 AC_SUBST(JAVAC)
+AC_SUBST(JAVA8)
 AC_SUBST(JAVAH)
 AC_SUBST(JAR)
 AC_SUBST(JVMLIBS)