scripts:prereqs: Add lit test prereqs

Add packages used by LLVM lit test.

Change-Id: I85f4ac0631abe358ce57c9081a071cf5ac00a486

install-prereqs.sh

diff --git a/install-prereqs.sh b/install-prereqs.sh
index e5763a4..c11c216 100755
--- a/install-prereqs.sh
+++ b/install-prereqs.sh
@@ -42,6 +42,7 @@
     libclang-dev
     libcunit1-dev
     libc6-dev
+    llvm-11-tools
     gcc
     g++
     gcc-10

python-requirements.txt

diff --git a/python-requirements.txt b/python-requirements.txt
index 0d41c52..48a093d 100644
--- a/python-requirements.txt
+++ b/python-requirements.txt
@@ -1,5 +1,6 @@
 camkes-deps
 hjson
+lit
 mako
 matplotlib
 netifaces