mkosi: Setup --ffile-prefix-map= for opensuse as well

This doesn't actually work because the opensuse spec doesn't allow
adding extra build flags, but I'm working on fixing that, so let's
already set things up for later.

mkosi.images/system/mkosi.conf.d/10-opensuse/mkosi.build.chroot

@@ -29,6 +29,20 @@ tee --append /usr/lib/rpm/suse/macros <<'EOF'
 %{nil}
 EOF
 
+VERSION="$(cat meson.version)"
+RELEASE="$(date "+%Y%m%d%H%M%S" --date "@$TS")"
+
+DIST="$(rpm --eval %dist)"
+ARCH="$(rpm --eval %_arch)"
+SRCDEST="/usr/src/debug/systemd-$VERSION-${RELEASE}${DIST}.$ARCH"
+
+# TODO: Enable this when the opensuse spec stops unconditionally setting FORTIFY_SOURCE=2.
+# EXTRA_CFLAGS="-O0 -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=0"
+EXTRA_CFLAGS=""
+if ((WITH_DEBUG)); then
+    EXTRA_CFLAGS="$EXTRA_CFLAGS -ffile-prefix-map=../src=$SRCDEST"
+fi
+
 build() {
     IFS=
     # TODO: Replace meson_build and meson_install overrides with "--undefine __meson_verbose" once
@@ -49,15 +63,17 @@ build() {
         $( ((WITH_DEBUG)) || echo --define) \
         $( ((WITH_DEBUG)) || echo "debug_package %{nil}") \
         --define "vendor openSUSE" \
-        --define "version_override $(cat meson.version)" \
-        --define "release_override $(date "+%Y%m%d%H%M%S" --date "@$TS")" \
+        --define "version_override $VERSION" \
+        --define "release_override $RELEASE" \
         --define "__check_files sh -c '$(rpm --eval %__check_files) | tee /tmp/unpackaged-files'" \
+        --define "build_cflags $(rpm --eval %build_cflags) $EXTRA_CFLAGS" \
         --define "meson_build %{shrink:%{__meson} compile -C %{_vpath_builddir} -j %{_smp_build_ncpus} %{nil}}" \
         --define "meson_install %{shrink:DESTDIR=%{buildroot} %{__meson} install -C %{_vpath_builddir} --no-rebuild --quiet %{nil}}" \
         --define "meson_extra_configure_options -D mode=developer -D b_sanitize=${SANITIZERS:-none}" \
         --define "__os_install_post /usr/lib/rpm/brp-suse %{nil}" \
         --define "__elf_exclude_path ^/usr/lib/systemd/tests/unit-tests/.*$" \
         --define "__script_requires %{nil}" \
+        --define "_find_debuginfo_dwz_opts %{nil}" \
         --noclean \
         "$@" \
         "pkg/$ID/systemd.spec"