Enable LTO in trusty modules

Adding flags to enable/disable LTO in trusty modules -
  - USER_LTO_ENABLED
  - KENREL_LTO_ENABLED

Bug: 157916058
Change-Id: I029ec39d46ab2a2a79c8428da5a47815a04dcc29
diff --git a/project/generic-arm-inc.mk b/project/generic-arm-inc.mk
index c9d9392..d14235d 100644
--- a/project/generic-arm-inc.mk
+++ b/project/generic-arm-inc.mk
@@ -80,6 +80,12 @@
 # limit physical memory to 38 bit to prevert tt_trampiline from getting larger than arm64_kernel_translation_table
 GLOBAL_DEFINES += MMU_IDENT_SIZE_SHIFT=38
 
+# enable LTO in user-tasks modules
+USER_LTO_ENABLED := true
+
+# enable LTO in kernel modules
+KENREL_LTO_ENABLED := true
+
 #
 # Modules to be compiled into lk.bin
 #