[PATCH 2/6] doc: sl-mx8mm: Add note about using cross toolchain

[Frieder Schrempf]

From: Frieder Schrempf <frieder.schrempf at kontron.de>

This clarifies the usage of a cross toolchain to build U-Boot
and TF-A.

Signed-off-by: Frieder Schrempf <frieder.schrempf at kontron.de>
---
 doc/board/kontron/sl-mx8mm.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/board/kontron/sl-mx8mm.rst b/doc/board/kontron/sl-mx8mm.rst
index 57143b973a..ff6f01d3b7 100644
--- a/doc/board/kontron/sl-mx8mm.rst
+++ b/doc/board/kontron/sl-mx8mm.rst
@@ -20,6 +20,12 @@ Quick Start
 - Build U-Boot
 - Boot
 
+.. note::
+
+   To build on a x86-64 host machine, you need a GNU cross toolchain for the
+   target architecture (aarch64). Check your distros package manager or
+   download and install the necessary tools (``aarch64-linux-gnu-*``) manually.
+
 Get and Build the Trusted Firmware-A (TF-A)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-- 
2.39.0