How to get values for rtlbootstrap.mk in configure?

[Tor Lillqvist]

> http://cgit.freedesktop.org/libreoffice/core/tree/sal/CustomTarget_generated.mk#n36
>
> That's probably not good.

If it is only for a MSVC build that it is empty, and it is a
MSVC-specific ifdef branch in a makefile that generates it empty, why
not just echo the relevant two lines into it in the makefile then
instead? f5ea2b5fa85660844daf092e84db45a759bf126d

--tml