toolchain: linker: Temp workaround for missing heap size info

At the moment there is no way to specify defines that should be passed
on to the linker when using the linker file generator. This is due to
the fact that for GCC they use the same executable for both compiling
and linking, and also that Zephyr uses a file to alloc the heap, but
IAR uses the linker to reserve a memory block instead, which is why it
requires the heap size info.

The thing that's actually causing the problem is the fact that if the
size of the heap is set to non-zero, there will be a heap variable of
the set size, but if size is zero the heap should take up as much
memory as it can.

To support both solutions, IAR need the size info for the link phase,
as that is where we can expand the heap to use the unallocated memory
when size is zero, but use the heap variable when size is non-zero.

My temporary solution is that when the heap size is not passed on
the command line to the IAR linker, we set it to zero and thus use as
much memory for the heap as possible. This solution should work for
now.

Signed-off-by: Lars-Ove Karlsson <lars-ove.karlsson@iar.com>

Author: LoveKarlsson

cmake/linker/iar/config_file_script.cmake

@@ -268,6 +268,9 @@ function(system_to_string)
   endforeach()
 
   if(IAR_LIBC)
+    set(${STRING_STRING} "${${STRING_STRING}}if (!isdefinedsymbol(K_HEAP_MEM_POOL_SIZE))\n{\n")
+    set(${STRING_STRING} "${${STRING_STRING}}  define symbol K_HEAP_MEM_POOL_SIZE=0;\n")
+    set(${STRING_STRING} "${${STRING_STRING}}}\n")
     set(${STRING_STRING} "${${STRING_STRING}}if (K_HEAP_MEM_POOL_SIZE>0)\n{\n")
     set(${STRING_STRING} "${${STRING_STRING}}  define block HEAP with alignment=8 { symbol kheap__system_heap };\n")
     set(${STRING_STRING} "${${STRING_STRING}}}\nelse\n{\n")