buildsystems: remove duplicate clause

This seems to have been there since 259d87c (Add scripts to
generate projects for other buildsystems (MSVC vcproj, QMake),
2009-09-16), i.e. since the beginning of that file.

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

contrib/buildsystems/engine.pl

@@ -265,7 +265,6 @@ sub handleCompileLine
             shift @parts;
         } elsif ("$part" eq "-c") {
             # ignore compile flag
-        } elsif ("$part" eq "-c") {
         } elsif ($part =~ /^.?-I/) {
             push(@incpaths, $part);
         } elsif ($part =~ /^.?-D/) {