Add packaging guide

Files have been ending up in differing places between distros - this is an attempt to fix this

Signed-off-by: Callum Farmer <gmbr3@opensuse.org>

docs/README.packaging.md

@@ -0,0 +1,19 @@
+# Packaging gnu-efi
+
+## Set variables per distro configuration
+
+make should be called with the following variables:
+
+- PREFIX (defaults to `/usr/local`)(`%{_prefix}` on RPM distros)
+- EXEC_PREFIX (*optional*) (defaults to `$PREFIX`) (`%{_exec_prefix}` on RPM distros)
+- LIBDIR (defaults to `$EXEC_PREFIX/lib`) (`%{_libdir}` on RPM distros)
+- INCLUDEDIR (*optional*) (defaults to `$PREFIX/include`) (`%{_includedir}` on RPM distros)
+- LINUX_HEADERS (**build only**) - location of Linux kernel header files - (*optional*) (defaults to `/usr/src/sys/build`)
+- DESTDIR (**install only**) - installation output directory (`%{buildroot}` on RPM distros - included in `%make_install`)
+
+Currently, these variables unless stated will need to be set for both build and installation stages.
+
+Those without optional markers I heavily suggest you to set them otherwise files may be located in the wrong directory
+for the architecture which you are building for
+
+*The related RPM variables are included here for cross referencing purposes*