fix: do not install ``docker-compose`` if already present

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

bin/myc-install

@@ -115,14 +115,16 @@ EOF
 ##
 ## We could need some docker-compose for some quick hacks
 ##
-# seems to require a C compiler
-apt-get install -y build-essential  </dev/null &&
-pip install wheel==0.33.6 &&
-pip install pip==19.3.1 cffi==1.12.3 subprocess32==3.5.4 texttable==1.6.2 \
-    pyrsistent==0.15.7 \
-    git+https://github.com/0k/compose@run_ignore_orphans || exit 1
-## Bug after updating pip
-hash -d pip || exit 1
+if ! type -p docker-compose >/dev/null; then
+    # seems to require a C compiler
+    apt-get install -y build-essential  </dev/null &&
+        pip install wheel==0.33.6 &&
+        pip install pip==19.3.1 cffi==1.12.3 subprocess32==3.5.4 texttable==1.6.2 \
+            pyrsistent==0.15.7 \
+            git+https://github.com/0k/compose@run_ignore_orphans || exit 1
+    ## Bug after updating pip
+    hash -d pip || exit 1
+fi
 
 if [ "$DOMAIN" ]; then
     sed -ri "s/^(\s+domain:\s+).*$/\1$DOMAIN/g" compose.yml