GNUARM.cmake: Support the CROSS_COMPILE setting

This is to support toolchains where the name is not arm-none-eabi-gcc,
such as arm-zephyr-eabi-gcc.

This is analogous to how it is solved in TFM.

Signed-off-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>
diff --git a/api-tests/CMakeLists.txt b/api-tests/CMakeLists.txt
index c243ebd..6181634 100644
--- a/api-tests/CMakeLists.txt
+++ b/api-tests/CMakeLists.txt
@@ -109,6 +109,11 @@
         HOST_GCC
 )
 
+# list of supported CROSS_COMPILE toolchains
+list(APPEND CROSS_COMPILE_TOOLCHAIN_SUPPORT
+        GNUARM
+)
+
 # list of suported CPU arch
 list(APPEND PSA_CPU_ARCH_SUPPORT
 	armv8m_ml
@@ -438,6 +443,9 @@
 
 # Check for supported toolchain/s
 if(${TOOLCHAIN} IN_LIST PSA_TOOLCHAIN_SUPPORT)
+        if(CROSS_COMPILE AND NOT (${TOOLCHAIN} IN_LIST CROSS_COMPILE_TOOLCHAIN_SUPPORT))
+                message(FATAL_ERROR "[PSA] : Error: CROSS_COMPILE not supported for this toolchain, supported toolchain are : ${CROSS_COMPILE_TOOLCHAIN_SUPPORT}")
+        endif()
         include(${PSA_ROOT_DIR}/tools/cmake/compiler/${TOOLCHAIN}.cmake)
 else()
         message(FATAL_ERROR "[PSA] : Error: Unsupported value for -DTOOLCHAIN=${TOOLCHAIN}, supported toolchain are : ${PSA_TOOLCHAIN_SUPPORT}")