mingw32: call lib.exe instead of lib to facilitate running it through wine.

Originally committed as revision 17995 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1599,7 +1599,7 @@ case $target_os in
         SLIBSUF=".dll"
         SLIBNAME_WITH_VERSION='$(SLIBPREF)$(FULLNAME)-$(LIBVERSION)$(SLIBSUF)'
         SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'
-        SLIB_EXTRA_CMD='-lib /machine:$(LIBTARGET) /def:$$(@:$(SLIBSUF)=.def) /out:$(SUBDIR)$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.lib)'
+        SLIB_EXTRA_CMD='-lib.exe /machine:$(LIBTARGET) /def:$$(@:$(SLIBSUF)=.def) /out:$(SUBDIR)$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.lib)'
         SLIB_INSTALL_EXTRA_CMD='-install -m 644 $(SUBDIR)$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.lib) "$(SHLIBDIR)/$(SLIBNAME:$(SLIBSUF)=.lib)"; \
             install -m 644 $(SUBDIR)$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.lib) "$(SHLIBDIR)/$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.lib)"'
         SLIB_UNINSTALL_EXTRA_CMD='rm -f "$(SHLIBDIR)/$(SLIBNAME:$(SLIBSUF)=.lib)"'