Add support for x86-64 microarchitecture levels

docker/Dockerfile.alpine

@@ -72,7 +72,11 @@ RUN echo "export CARGO_TARGET=${RUST_MUSL_CROSS_TARGET}" >> /env-cargo && \
     cat /env-cargo
 
 RUN source /env-cargo && \
-    rustup target add "${CARGO_TARGET}"
+    rustup target add "${CARGO_TARGET}" && \
+    # Set target CPU to the specified x86-64 microarchitecture level (if present)
+    if [[ "${TARGETARCH}${TARGETVARIANT}" == amd64v* ]] ; then echo "export RUSTFLAGS='-Ctarget_cpu=x86-64-${TARGETVARIANT}'" >> /env-cargo ; fi && \
+    # Output the current contents of the file
+    cat /env-cargo
 
 # Copies over *only* your manifests and build files
 COPY ./Cargo.* ./rust-toolchain.toml ./build.rs ./

docker/Dockerfile.debian

@@ -112,7 +112,11 @@ RUN source /env-cargo && \
     cat /env-cargo
 
 RUN source /env-cargo && \
-    rustup target add "${CARGO_TARGET}"
+    rustup target add "${CARGO_TARGET}" && \
+    # Set target CPU to the specified x86-64 microarchitecture level (if present)
+    if [[ "${TARGETARCH}${TARGETVARIANT}" == amd64v* ]] ; then echo "export RUSTFLAGS='-Ctarget_cpu=x86-64-${TARGETVARIANT}'" >> /env-cargo ; fi && \
+    # Output the current contents of the file
+    cat /env-cargo
 
 # Copies over *only* your manifests and build files
 COPY ./Cargo.* ./rust-toolchain.toml ./build.rs ./

docker/Dockerfile.j2

@@ -139,7 +139,11 @@ RUN echo "export CARGO_TARGET=${RUST_MUSL_CROSS_TARGET}" >> /env-cargo && \
 
 {% endif %}
 RUN source /env-cargo && \
-    rustup target add "${CARGO_TARGET}"
+    rustup target add "${CARGO_TARGET}" && \
+    # Set target CPU to the specified x86-64 microarchitecture level (if present)
+    if [[ "${TARGETARCH}${TARGETVARIANT}" == amd64v* ]] ; then echo "export RUSTFLAGS='-Ctarget_cpu=x86-64-${TARGETVARIANT}'" >> /env-cargo ; fi && \
+    # Output the current contents of the file
+    cat /env-cargo
 
 # Copies over *only* your manifests and build files
 COPY ./Cargo.* ./rust-toolchain.toml ./build.rs ./