dockerfile: Separate layer for removing kernel + initrd

Baseconfigs tests were failing in CI because the initrd which had the
expected baseconfigs was being deleted in the same layer it was being
created in. Move the deletion to a completely separate layer

Signed-off-by: Pragyan Poudyal <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

Dockerfile

@@ -221,7 +221,7 @@ COPY --from=update-generated-from-code /src/docs/src/*.schema.json /docs/src/
 # ----
 
 # Perform all filesystem transformations except generating the sealed UKI (if configured)
-FROM base as base-penultimate-source
+FROM base as base-source
 ARG variant
 ARG bootloader
 ARG boot_type
@@ -251,7 +251,7 @@ rm -rf /run/rhsm
 
 EORUN
 
-FROM base-penultimate-source as base-penultimate
+FROM base-source as base-penultimate-source
 ARG boot_type
 
 # Configure the rootfs
@@ -272,9 +272,14 @@ RUN --network=none --mount=type=tmpfs,target=/run --mount=type=tmpfs,target=/tmp
 COPY --from=packaging /usr-extras/ /usr/
 # Clean up package manager caches
 RUN --network=none --mount=type=tmpfs,target=/run --mount=type=tmpfs,target=/tmp \
-    --mount=type=bind,from=base-penultimate-source,src=/,target=/run/base-penultimate-src \
     --mount=type=bind,from=packaging,src=/,target=/run/packaging <<EORUN
     /run/packaging/cleanup
+EORUN
+
+FROM base-penultimate-source as base-penultimate
+RUN --network=none --mount=type=tmpfs,target=/run --mount=type=tmpfs,target=/tmp \
+    --mount=type=bind,from=base-penultimate-source,src=/,target=/run/base-penultimate-src \
+    --mount=type=bind,from=packaging,src=/,target=/run/packaging <<EORUN
 
     # Remove kernel + initrd if UKI
     if [[ "${boot_type}" == "uki" ]]; then