Make cargo new independent of workdir to be exact

The muslrust images seem to have a workdir of /volume as opposed to / in the
others so doing cargo new like this would create the folder in /volume/app.

docker/amd64/sqlite/Dockerfile

@@ -38,7 +38,7 @@ ARG DB=sqlite
 RUN rustup set profile minimal
 
 # Creates a dummy project used to grab dependencies
-RUN USER=root cargo new --bin app
+RUN USER=root cargo new --bin /app
 WORKDIR /app
 
 # Copies over *only* your manifests and build files

docker/amd64/sqlite/Dockerfile.alpine

@@ -33,7 +33,7 @@ RUN rustup set profile minimal
 ENV USER "root"
 
 # Creates a dummy project used to grab dependencies
-RUN USER=root cargo new --bin app
+RUN USER=root cargo new --bin /app
 WORKDIR /app
 
 # Copies over *only* your manifests and build files