Add libjpeg-dev because Pillow wants it

Change-Id: I0b1afd8fce5d7a800aab74ed3cb350e3536e0f40

install-prereqs.sh

diff --git a/install-prereqs.sh b/install-prereqs.sh
index adfd5b4..50d8451 100755
--- a/install-prereqs.sh
+++ b/install-prereqs.sh
@@ -56,6 +56,7 @@
     libglib2.0-dev
     libglib2.0-dev-bin
     libgtk2.0-0
+    libjpeg-dev
     libmpfr-dev
     libpixman-1-dev
     libpython3-dev