Disassemble blocks of zeroes

This commit adds the "--disassemble-zeroes" option to objdump command to
make it easier to see usages of hardened check macros.

Signed-off-by: Alphan Ulusoy <alphan@google.com>
diff --git a/sw/device/meson.build b/sw/device/meson.build
index 044e756..1edf688 100644
--- a/sw/device/meson.build
+++ b/sw/device/meson.build
@@ -19,6 +19,7 @@
     '--disassemble',
     '--headers',
     '--line-numbers',
+    '--disassemble-zeroes',
     '--source',
     '@INPUT@',
   ],