Guys
FYI
Although I managed to pass a symbol (define) into the linker script, I've now found that symbols are not supported in MEMORY section definitions in linker scripts
There seem to be some hacking work arounds that may work in one version of LD but they don't seem to be a stable way to do this.
But thinking about it, there may be another way, by concatenating the processor type and another flag / variable in the boards.txt file to defined the file name of the linker script.
i.e
stm32f103re_bootloader.ld
and stm32f103re_no_bootloader.ld
made of
"stm32f103re" and "_bootloader" or "no_bootloader"
I will see if that works, and let you know.
(I just thought I'd post in case anyone else decided to look at this in the future and think they could use symbols in the linker script for MEMORY definitions )