[OE-core] Make sstate cache local tool independent

[Richard Purdie]

On Fri, 2014-01-31 at 09:08 +0100, Mike Looijmans wrote:
> I'm forced to using external tools in some recipes (that build FPGA bitstreams 
> using huge proprietary packages). Building these takes between half an hour 
> and several hours on big fast machines, so I definitely want to use 
> sstate-cache for these.
> 
> The trouble I'm running into is that I have a variable like XILINX_TOOL_PATH 
> which is in local.conf so people can tell where the tools are.
> 
> The compile part of the recipe runs something like 
> ${XILINX_TOOL_PATH}/bin/something
> 
> This makes the "compile" step dependent on that variable. When a machine 
> installs the tools somewhere else, it will have a different value for that 
> tool, and because OE thinks that matters, it will insist on building its very 
> own version of that package instead of just fetching it from the sstate-cache 
> on the buildserver.
> 
> How do I explain to OE that the value of this variable does not matter for the 
> sstate-cache?
> 
> I tried: do_compile[vardepsexclude] = "XILINX_TOOL_PATH"
> 
> that didn't appear to help.

Is the name of the compile step do_compile, or are there intermediate
functions?

vardepsexclude should work but you need to make sure you apply it to the
right variable/function.

Cheers,

Richard