Docs: Rearrange TF-M building instructions

- move the building instructios to a dedicated folder, reflecting main TOC
- adjust links in the documentation

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I335de95061938d619a47cd813020121809e1459b
diff --git a/docs/contributing/contributing_process.rst b/docs/contributing/contributing_process.rst
index 3eb6cdf..04cea4c 100644
--- a/docs/contributing/contributing_process.rst
+++ b/docs/contributing/contributing_process.rst
@@ -20,7 +20,7 @@
   - Clone the TF-M code on your own machine from `TF-M git repository
     <https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git>`_.
   - Follow the :doc:`TF-M getting started </getting_started/tfm_getting_started>`,
-    :doc:`Build Instructions </technical_references/instructions/tfm_build_instruction>` and
+    :doc:`Build Instructions </building/tfm_build_instruction>`
     :doc:`Coding Guide </contributing/coding_guide>` for the TF-M project.
   - Make your changes in logical chunks to help reviewers. Each commit should
     be a separate review and either work properly or be squashed after the