Recommend the installation of wheel

Wheel is a binary distribution mechanism for Python packages, used by
pip. Not having wheel installed can cause users to install less powerful
versions of Python packages (and it causes a lot of warnings during `pip
install`).

Signed-off-by: Philipp Wagner <phw@lowrisc.org>
diff --git a/apt-requirements.txt b/apt-requirements.txt
index 2590650..17b85d4 100644
--- a/apt-requirements.txt
+++ b/apt-requirements.txt
@@ -23,6 +23,7 @@
 python3
 python3-pip
 python3-setuptools
+python3-wheel
 srecord
 tree
 zlib1g-dev