Build: Split build v2 for an521 platform

Please refer to the updated Regression tests in tf-m-tests repository
in "feature-build-split-v2" branch for an example of how to use
Split build.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Signed-off-by: Dávid Házi <david.hazi@arm.com>
Change-Id: Ie07541b95ad38e38115a1d59544707035fd4c1d6
diff --git a/interface/CMakeLists.txt b/interface/CMakeLists.txt
index f3434e2..2c431c6 100644
--- a/interface/CMakeLists.txt
+++ b/interface/CMakeLists.txt
@@ -28,9 +28,9 @@
 
 target_include_directories(psa_interface
     INTERFACE
-        ${CMAKE_CURRENT_SOURCE_DIR}/include
-        ${CMAKE_BINARY_DIR}/generated/interface/include
-        $<$<BOOL:${TFM_MULTI_CORE_TOPOLOGY}>:${CMAKE_CURRENT_SOURCE_DIR}/include/multi_core>
+        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+        $<BUILD_INTERFACE:${CMAKE_BINARY_DIR}/generated/interface/include>
+        $<BUILD_INTERFACE:$<$<BOOL:${TFM_MULTI_CORE_TOPOLOGY}>:${CMAKE_CURRENT_SOURCE_DIR}/include/multi_core>>
 )
 
 target_link_libraries(psa_interface