build_packages: Build multiple packages in one go when breaking loops

Instead of rebuilding just one package and maybe rebuilding others as
a fallout, force rebuilding all the mentioned packages. This makes the
build process a bit more robust against package build ordering
changes.

May be useful when breaking multiple dep loops that have some common
packages, so we build them all once.

build_packages

@@ -186,44 +186,82 @@ fi
 # Goo to attempt to resolve dependency loops on individual packages.
 # If this becomes insufficient we will need to move to a full multi-stage
 # bootstrap process like we do with the SDK via catalyst.
+#
+# Called like:
+#
+#     break_dep_loop [PKG_USE_PAIR]…
+#
+# PKG_USE_PAIR consists of two arguments: a package name (for example:
+# sys-fs/lvm2), and a comma-separated list of USE flags to clear (for
+# example: udev,systemd).
 break_dep_loop() {
-  local pkg="$1"
-  local flags=( ${2//,/ } )
-  shift 2
+  local -a pkgs
+  local -a all_flags
+  local -a args
   local flag_file="${BOARD_ROOT}/etc/portage/package.use/break_dep_loop"
+  local -a flag_file_entries
+  local -a pkg_summaries
 
   # Be sure to clean up use flag hackery from previous failed runs
   sudo rm -f "${flag_file}"
 
-  # If the package is already installed we have nothing to do
-  if portageq-"${BOARD}" has_version "${BOARD_ROOT}" "${pkg}"; then
-    return 0
+  if [[ $# -eq 0 ]]; then
+      return 0
   fi
 
-  # Likewise, nothing to do if the flag isn't actually enabled.
-  if ! pkg_use_enabled "${pkg}" "${flags[@]}"; then
-    return 0
-  fi
-
-  # Temporarily compile/install package with flag disabled. If a binary
+  # Temporarily compile/install packages with flags disabled. If a binary
   # package is available use it regardless of its version or use flags.
-  local disabled_flags="${flags[@]/#/-}"
-  info "Merging ${pkg} with USE=${disabled_flags}"
-  sudo mkdir -p "${flag_file%/*}"
-  sudo_clobber "${flag_file}" <<<"${pkg} ${disabled_flags}"
-  # Disable any other problematic flags
-  extra_args=""
+  local pkg
+  local -a flags
+  local disabled_flags
   while [[ $# -gt 0 ]]; do
-      sudo_append "${flag_file}" <<<"$1 -$2"
-      extra_args+=" --buildpkg-exclude=$1 --useoldpkg-atoms=$1"
-      shift 2
+    pkg="${1}"
+    pkgs+=("${pkg}")
+    flags=( ${2//,/ } )
+    all_flags+=("${flags[@]}")
+    disabled_flags="${flags[@]/#/-}"
+    flag_file_entries+=("${pkg} ${disabled_flags}")
+    args+=("--buildpkg-exclude=${pkg}")
+    pkg_summaries+=("${pkg}[${disabled_flags}]")
+    shift 2
+  done
+
+  # If packages are already installed we have nothing to do
+  local any_package_uninstalled=0
+  for pkg in "${pkgs[@]}"; do
+    if ! portageq-"${BOARD}" has_version "${BOARD_ROOT}" "${pkgs[@]}"; then
+      any_package_uninstalled=1
+      break
+    fi
+  done
+  if [[ ${any_package_uninstalled} -eq 0 ]]; then
+    return 0
+  fi
+
+  # Likewise, nothing to do if the flags aren't actually enabled.
+  local any_flag_enabled=0
+  for pkg in "${pkgs[@]}"; do
+    if pkg_use_enabled "${pkg}" "${all_flags[@]}"; then
+      any_flag_enabled=1
+      break
+    fi
+  done
+  if [[ ${any_flag_enabled} -eq 0 ]]; then
+    return 0
+  fi
+
+  info "Merging ${pkg_summaries[@]}"
+  sudo mkdir -p "${flag_file%/*}"
+  sudo_clobber "${flag_file}" <<<"${flag_file_entries[0]}"
+  local entry
+  for entry in "${flag_file_entries[@]:1}"; do
+    sudo_append "${flag_file}" <<<"${entry}"
   done
   # rebuild-if-unbuilt is disabled to prevent portage from needlessly
   # rebuilding zlib for some unknown reason, in turn triggering more rebuilds.
   sudo -E "${EMERGE_CMD[@]}" "${EMERGE_FLAGS[@]}" \
-      --rebuild-if-unbuilt=n \
-      --buildpkg-exclude="${pkg}" \
-      ${extra_args} "${pkg}"
+    --rebuild-if-unbuilt=n \
+    "${args[@]}" "${pkgs[@]}"
   sudo rm -f "${flag_file}"
 }