Install libdw-dev so dpkg-checkbuilddeps passes (amd64 + arm64)

The kernel's generated debian/control lists libdw-dev:native as an
unconditional Build-Depends, so dpkg-buildpackage aborts via
dpkg-checkbuilddeps before the build starts -- regardless of .config.
Disabling BTF/pahole never satisfied this check.

libdw-dev is just the elfutils libdw headers and does not make pahole
run; dwarves stays absent since DEBUG_INFO_BTF is disabled.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -132,12 +132,16 @@ jobs:
         if: env.BUILD_NEEDED == 'true'
         run: |
           sudo apt-get update
-          # dwarves/libdw-dev (pahole) are intentionally absent: the build sets
-          # CONFIG_DEBUG_INFO_NONE=y and DEBUG_INFO_BTF=n (see prepare-kernel-config.sh),
-          # so pahole never runs. Re-add them if BTF is ever enabled.
+          # libdw-dev is an unconditional Build-Depends in the kernel's generated
+          # debian/control (scripts/package/mkdebian), so dpkg-checkbuilddeps aborts
+          # the build without it -- even though we disable BTF. It's just the elfutils
+          # libdw headers and does NOT make pahole run.
+          # dwarves (pahole) stays absent: the build sets CONFIG_DEBUG_INFO_NONE=y and
+          # DEBUG_INFO_BTF=n (see prepare-kernel-config.sh), so pahole never runs.
+          # Re-add dwarves if BTF is ever enabled.
           sudo apt-get install -y \
             git build-essential \
-            libncurses-dev libssl-dev libelf-dev \
+            libncurses-dev libssl-dev libelf-dev libdw-dev \
             bison bc flex rsync debhelper \
             dpkg-dev fakeroot kmod cpio \
             lz4 zstd xz-utils curl jq