build: use local libstrophe version and limit depth

`--depth 1` flag ensures that only latest version is loaded (since there is no need to sync full git)
Using local libstrophe version increases speed of fetching

Dockerfile.debian

@@ -36,7 +36,7 @@ RUN mkdir -p /usr/src/{stabber,libstrophe,profanity}
 WORKDIR /usr/src
 
 #RUN git clone https://github.com/boothj5/stabber
-RUN git clone -c http.sslverify=false https://github.com/strophe/libstrophe
+RUN git clone --depth 1 https://git.jabber.space/devs/libstrophe-gh.git libstrophe
 
 #WORKDIR /usr/src/stabber
 #RUN ./bootstrap.sh