This fixes issues building in a tree which has symlinks in its path,
for some reason PROJECT_BASE ends up having symlinks removed from it
but not ZEPHYR_BASE, causing Python to generate relative paths
with "../.." (for example) in the beginning. This patch ensures both
have symlinks removed before computing SOURCE_DIR.
Change-Id: I3e0688b602a320d7644834b73cde79cfe91cb677
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>