sencha: add sim_cheriot_renode to run standalone cheriot firmware

Adds a shell function sim_cheriot_renode that runs a firmware image in
a standalone renode environment.

Bypass-Presubmit-Reason: no sencha CI tests

Change-Id: I687a43cd519a5f56425941d0535fc332a5bb3fc0

platforms/sencha/setup.sh

diff --git a/platforms/sencha/setup.sh b/platforms/sencha/setup.sh
index 1da8111..74bb612 100644
--- a/platforms/sencha/setup.sh
+++ b/platforms/sencha/setup.sh
@@ -92,3 +92,13 @@
         --disable-xwt --console)
 
 }
+
+function sim_cheriot_renode
+{
+    # Run the ELF firmware with renode
+    local elf_file="$(realpath $1)"
+
+    (cd "${ROOTDIR}" && renode -e "\$bin=@${elf_file}; \
+        i @sim/config/cheriot.resc; start" \
+        --disable-xwt --console)
+}