Build: Added option to treat warnings as errors

Useful for CI.

Change-Id: I68b5acc949de69f1f7fb502bdc8efbbb659c3155
Signed-off-by: Bohdan Hunko <Bohdan.Hunko@infineon.com>
diff --git a/toolchain_IARARM.cmake b/toolchain_IARARM.cmake
index 83156fe..bf0f35f 100644
--- a/toolchain_IARARM.cmake
+++ b/toolchain_IARARM.cmake
@@ -61,6 +61,7 @@
     $<$<COMPILE_LANGUAGE:C,CXX>:--diag_suppress=Pe546,Pe940,Pa082,Pa084>
     $<$<COMPILE_LANGUAGE:C,CXX>:--no_path_in_file_macros>
     $<$<AND:$<COMPILE_LANGUAGE:C,CXX,ASM>,$<BOOL:${TFM_DEBUG_SYMBOLS}>,$<CONFIG:Release,MinSizeRel>>:-r>
+    $<$<AND:$<COMPILE_LANGUAGE:C,CXX>,$<BOOL:${CONFIG_TFM_WARNINGS_ARE_ERRORS}>>:--warnings_are_errors>
 )
 
 add_link_options(