Docs: Fixes building instructions

Fixes the building instructions for AN521 regression sample tests.

Signed-off-by: Matthew Dalzell <matthew.dalzell@arm.com>
Change-Id: I185760ea83c48912de0f4e7b39b290ea20e6cc89
diff --git a/docs/getting_started/tfm_getting_started.rst b/docs/getting_started/tfm_getting_started.rst
index b9dace5..d013760 100644
--- a/docs/getting_started/tfm_getting_started.rst
+++ b/docs/getting_started/tfm_getting_started.rst
@@ -265,7 +265,7 @@
             cmake --build build_spe -- install
 
             cmake -S . -B build_test -DCONFIG_SPE_PATH=<absolute path to>/build_spe/api_ns \
-                  -DCMAKE_BUILD_TYPE=Debug -DTFM_TOOLCHAIN_FILE=<Absolute path to>/toolchain_GNUARM.cmake
+                  -DCMAKE_BUILD_TYPE=Debug -DTFM_TOOLCHAIN_FILE=<Absolute path to>/toolchain_ns_GNUARM.cmake
             cmake --build build_test
 
     .. group-tab:: Windows
@@ -291,7 +291,7 @@
             cmake --build build_spe -- install
 
             cmake -G"Unix Makefiles" -S . -B build_test -DCONFIG_SPE_PATH=<absolute path to>/build_spe/api_ns \
-                  -DCMAKE_BUILD_TYPE=Debug -DTFM_TOOLCHAIN_FILE=<Absolute path to>/toolchain_GNUARM.cmake
+                  -DCMAKE_BUILD_TYPE=Debug -DTFM_TOOLCHAIN_FILE=<Absolute path to>/toolchain_ns_GNUARM.cmake
             cmake --build build_test
 
         .. note::