patch 8.2.2104: build problem with Ruby 2.7

Problem:    Build problem with Ruby 2.7.
Solution:   Adjust function declarations. (Ozaki Kiichi, closes #7430)
diff --git a/src/auto/configure b/src/auto/configure
index 205312a..ef1acd8 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -7617,8 +7617,7 @@
 	librubyarg=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['LIBRUBYARG'])"`
 	librubya=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['LIBRUBY_A'])"`
 	rubylibdir=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['libdir'])"`
-	if test -f "$rubylibdir/$librubya"; then
-	  librubyarg="$librubyarg"
+	if test -f "$rubylibdir/$librubya" || expr "$librubyarg" : "-lruby"; then
 	  RUBY_LIBS="$RUBY_LIBS -L$rubylibdir"
 	elif test "$librubyarg" = "libruby.a"; then
 	  	  librubyarg="-lruby"