build: add qt client link to build instructions

The build manual does not contain the build instructions. This commit
adds a link to jami-client-qt's INSTALL.md, which is where the build
instructions are.

Change-Id: I45edd60c5dc5bdb14f20a166130ab94fb33ba719

build/dependencies.rst

@@ -101,6 +101,11 @@ repository.
 jami-client-qt
 --------------
 
+.. note:: For complete instructions on how to build the Qt client,
+          please refer to te the `INSTALL.md
+          <https://git.jami.net/savoirfairelinux/jami-client-qt/-/blob/master/INSTALL.md>`_
+          file.
+
 Building the Jami client currently requires the following tools and
 libraries: