Add missing pyelftools dependency to builder image

libkrunfw's bin2cbundle.py imports elftools (pyelftools) to
convert the compiled kernel ELF into a C bundle.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: JAORMX

images/builder/Containerfile

@@ -19,7 +19,7 @@ RUN dnf install -y \
         golang \
         rust cargo \
         clang \
-        make gcc flex bison elfutils-libelf-devel bc openssl-devel perl diffutils python3 cpio git pkg-config patchelf patch \
+        make gcc flex bison elfutils-libelf-devel bc openssl-devel perl diffutils python3 python3-pyelftools cpio git pkg-config patchelf patch \
         virtiofsd libseccomp-devel glib2-devel zlib-devel \
     && dnf clean all