add a distro config for MacOSX 64 bits build (10.8 min sdk)

Change-Id: I21fbfce72cdf7446845df8ae8f65d6d899163d2f

distro-configs/LibreOfficeMacOSX64.conf

+--with-vendor=The Document Foundation
+--enable-64-bit
+--enable-epm
+--enable-scripting-beanshell
+--enable-scripting-javascript
+--enable-ext-wiki-publisher
+--enable-ext-nlpsolver
+--enable-extension-integration
+--enable-online-update
+--without-system-postgresql
+--disable-gtk
+--with-help
+--with-myspell-dicts
+--with-package-format=dmg
+--with-macosx-sdk=10.8
+--with-macosx-version-min-required=10.8