configure: use dashes instead of slashes in lib.exe invocation

This avoids issues with wrong parameter translation by msys on some systems,
and the Windows SDK tools accept both forms equally.

configure

@@ -4804,7 +4804,7 @@ case $target_os in
         SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'
         dlltool="${cross_prefix}dlltool"
         if check_cmd lib.exe -list; then
-            SLIB_EXTRA_CMD=-'sed -e "s/ @[^ ]*//" $$(@:$(SLIBSUF)=.orig.def) > $$(@:$(SLIBSUF)=.def); lib.exe /nologo /machine:$(LIBTARGET) /def:$$(@:$(SLIBSUF)=.def) /out:$(SUBDIR)$(SLIBNAME:$(SLIBSUF)=.lib)'
+            SLIB_EXTRA_CMD=-'sed -e "s/ @[^ ]*//" $$(@:$(SLIBSUF)=.orig.def) > $$(@:$(SLIBSUF)=.def); lib.exe -nologo -machine:$(LIBTARGET) -def:$$(@:$(SLIBSUF)=.def) -out:$(SUBDIR)$(SLIBNAME:$(SLIBSUF)=.lib)'
             if enabled x86_64; then
                 LIBTARGET=x64
             fi