build: Ensure we are copying the correct binary for docker container

Dockerfile

@@ -1,8 +1,6 @@
 FROM rust:1.80 AS builder
 ARG TARGETPLATFORM
 USER 1000
-WORKDIR /usr/src/
-
 RUN if [ "$TARGETPLATFORM" = "linux/amd64" ]; then  \
     rustup target add x86_64-unknown-linux-musl;  \
     elif [ "$TARGETPLATFORM" = "linux/arm/v7" ]; then  \
@@ -12,11 +10,10 @@ RUN if [ "$TARGETPLATFORM" = "linux/amd64" ]; then  \
     else exit 1;  \
     fi
 
-WORKDIR /usr/src/whatismyip
+WORKDIR /app/whatismyip
 COPY . ./
 
-RUN --mount=type=cache,target=/usr/src/whatismyip/target \
-    if [ "$TARGETPLATFORM" = "linux/amd64" ]; then  \
+RUN if [ "$TARGETPLATFORM" = "linux/amd64" ]; then  \
     cargo build --target=x86_64-unknown-linux-musl --release ;  \
     elif [ "$TARGETPLATFORM" = "linux/arm/v7" ]; then  \
     cargo build --target=armv7-unknown-linux-musleabihf --release ;  \
@@ -25,19 +22,9 @@ RUN --mount=type=cache,target=/usr/src/whatismyip/target \
     else exit 1;  \
     fi
 
-RUN --mount=type=cache,target=/usr/src/whatismyip/target \
-    if [ "$TARGETPLATFORM" = "linux/amd64" ]; then  \
-    cargo install --target=x86_64-unknown-linux-musl --path . ;  \
-    elif [ "$TARGETPLATFORM" = "linux/arm/v7" ]; then  \
-    cargo install --target=armv7-unknown-linux-musleabihf --path . ;  \
-    elif [ "$TARGETPLATFORM" = "linux/arm64" ]; then  \
-    cargo install --target=aarch64-unknown-linux-musl --path . ;  \
-    else exit 1;  \
-    fi
-
 # Bundle Stage
 FROM scratch
-COPY --from=builder /usr/local/cargo/bin/whatismyip .
+COPY --from=builder /app/whatismyip/target/*/release/whatismyip .
 RUN ["./whatismyip", "-l"]
 USER 1000
 ENTRYPOINT ["./whatismyip"]