contrib/buildsystems: handle libiconv, too

Git's test suite shows tons of breakages unless Git is compiled
*without* NO_ICONV. That means, in turn, that we need to generate
build definitions *with* libiconv, which in turn implies that we
have to handle the -liconv option properly.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

contrib/buildsystems/engine.pl

@@ -345,6 +345,8 @@ sub handleLinkLine
             push(@libs, "ssleay32.lib");
         } elsif ("$part" eq "-lcurl") {
             push(@libs, "libcurl.lib");
+        } elsif ("$part" eq "-liconv") {
+            push(@libs, "libiconv.lib");
         } elsif ($part =~ /^-/) {
             push(@lflags, $part);
         } elsif ($part =~ /\.(a|lib)$/) {