Only pass --global-base to the linker if its set to a non-default value

Otherwise rely on the linker default value of 1024.

This change is in preparation of using `--stack-first` in debug builds.
When `--stack-first` is passed to the linker `--global-base` is ignored
(it should really be an error do this).

I also avoid needless passing redundant arguments to the linker.

tools/building.py

diff --git a/tools/building.py b/tools/building.py
index 4a41742..2ba36b1 100644
--- a/tools/building.py
+++ b/tools/building.py
@@ -225,7 +225,7 @@
       cmd.append('--max-memory=%d' % settings.INITIAL_MEMORY)
     elif settings.MAXIMUM_MEMORY != -1:
       cmd.append('--max-memory=%d' % settings.MAXIMUM_MEMORY)
-    if not settings.RELOCATABLE:
+    if settings.GLOBAL_BASE != 1024 and not settings.RELOCATABLE:
       cmd.append('--global-base=%s' % settings.GLOBAL_BASE)
 
   return cmd