luaposix: disable documentation build

Lost when luaposix converted their upstream build system.
Required to prevent the build from attempting to invoke "ldoc" on the
host and also simply to speed it up.

Signed-off-by: Karl Palsson <karlp@tweak.net.au>

lang/luaposix/patches/900-disable-ldoc.patch

@@ -0,0 +1,13 @@
+diff --git a/lukefile b/lukefile
+index 2d4bb2f..1e48540 100644
+--- a/lukefile
++++ b/lukefile
+@@ -29,8 +29,6 @@ incdirs  = {
+    '$LUA_INCDIR',
+ }
+ 
+-ldocs    = 'build-aux/config.ld.in'
+-
+ modules  = {
+    ['posix']               = 'lib/posix/init.lua',
+    ['posix._base']         = 'lib/posix/_base.lua',