lua: fix dynamic library install

lua: fix dynamic library install

In 0002-shared-libs-for-lua.patch, revision number is used to set
library name:
TO_SOLIB = liblua.so.$(R)

However, library is built using PKG_VERSION which is passed only during
build step:
$(CC) -o $@.$(PKG_VERSION) -shared -Wl,-soname="$@.$(PKG_VERSION)" $?

As a result, dynamic library is not installed in staging or target paths
since bump to lua 5.3.5

So, instead of replacing R by PKG_VERSION and passing this variable in
all steps, simply update R to 5

Fixes:
 - http://autobuild.buildroot.net/results/28b6672188bb0082ac1467d3b45904880e3634f3

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Acked-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Fabrice Fontaine &lt;<a href="mailto:fontaine.fabrice@gmail.com" target="_blank">fontaine.fabrice@gmail.com</a>&gt;<br></blockquote><div><br></div><div>Acked-by: Francois Perrad &lt;<a href="mailto:francois.perrad@gadz.org" target="_blank">francois.perrad@gadz.org</a>&gt;</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>