eclass/toolchain.eclass: mask LIBPATH for cross-case, bug #692844

/usr/lib/gcc/${CTARGET}/${GCC_CONFIG_VER} contains libraries
destined to be used by ${CTARGET}. revdep-rebuild complains
about missing dependencies against them as we don't populate
LDPATH (or anything else) for them.

The change populates /etc/revdep-rebuild/05cross-${CTARGET}-${GCC_CONFIG_VER}
with a single entry:
    SEARCH_DIRS_MASK="/usr/lib/gcc/${CTARGET}/${GCC_CONFIG_VER}"

crossdev will still own root's SEARCH_DIRS_MASK="/usr/${CTARGET}".

Reported-by: crocket
Closes: https://bugs.gentoo.org/692844
Signed-off-by: Sergei Trofimovich <[email protected]>

eclass/toolchain.eclass

@@ -1818,6 +1818,7 @@ toolchain_src_install() {
 
  dodir /etc/env.d/gcc
  create_gcc_env_entry
+ create_revdep_rebuild_entry
 
  # Setup the gcc_env_entry for hardened gcc 4 with minispecs
  want_minispecs && copy_minispecs_gcc_specs
@@ -2138,6 +2139,20 @@ create_gcc_env_entry() {
  EOF
 }
 
+create_revdep_rebuild_entry() {
+ dodir /etc/revdep-rebuild
+ local revdep_rebuild_base="/etc/revdep-rebuild/05cross-${CTARGET}-${GCC_CONFIG_VER}"
+ local revdep_rebuild_file="${ED}${revdep_rebuild_base}"
+
+ is_crosscompile || return 0
+
+ cat <<-EOF > ${revdep_rebuild_file}
+ # Generated by ${CATEGORY}/${PF}
+ # Ignore libraries built for ${CTARGET}, https://bugs.gentoo.org/692844.
+ SEARCH_DIRS_MASK="${LIBPATH}"
+ EOF
+}
+
 copy_minispecs_gcc_specs() {
  # on gcc 6 we don't need minispecs
  if tc_version_is_at_least 6.0 ; then