Add CMake option for explicitly link library to trusted_storage (#2)

option name: LINK_WITH_TRUSTED_STORAGE
default value: ON
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 6b2a850..cbbaf06 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -1,6 +1,7 @@
 option(USE_STATIC_MBEDTLS_LIBRARY "Build mbed TLS static library." ON)
 option(USE_SHARED_MBEDTLS_LIBRARY "Build mbed TLS shared library." OFF)
 option(LINK_WITH_PTHREAD "Explicitly link mbed TLS library to pthread." OFF)
+option(LINK_WITH_TRUSTED_STORAGE "Explicitly link mbed TLS library to trusted_storage." ON)
 
 # Set the project root directory if it's not already defined, as may happen if
 # the library folder is included directly by a parent project, without
@@ -125,6 +126,10 @@
     set(libs ${libs} pthread)
 endif()
 
+if(LINK_WITH_TRUSTED_STORAGE)
+    set(libs ${libs} trusted_storage)
+endif()
+
 if (NOT USE_STATIC_MBEDTLS_LIBRARY AND NOT USE_SHARED_MBEDTLS_LIBRARY)
     message(FATAL_ERROR "Need to choose static or shared mbedtls build!")
 endif(NOT USE_STATIC_MBEDTLS_LIBRARY AND NOT USE_SHARED_MBEDTLS_LIBRARY)