configure: Disable PIC for cygwin just as for win32/mingw

If this is explicitly disabled for win32/mingw, it should also
be disabled for cygwin, for consistency and for the same reasons
as for win32/mingw.

Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -3084,6 +3084,7 @@ case $target_os in
         SHFLAGS='-shared -Wl,--out-implib,$(SUBDIR)lib$(FULLNAME).dll.a'
         objformat="win32"
         enable dos_paths
+        disable pic
         ;;
     *-dos|freedos|opendos)
         network_extralibs="-lsocket"