pfunct: Use languages__init() to honour PAHOLE_LANG_EXCLUDE

  $ echo $PAHOLE_LANG_EXCLUDE

  $ pfunct -F dwarf `pahole --running_kernel_vmlinux` > /dev/null
  die__process_class: tag not supported 0x33 (variant_part) at <7719ef8>!
  die__create_new_enumeration: DW_TAG_subprogram (0x2e) @ <0x77370f1> not handled in a rust CU!
  tag__recode_dwarf_type: couldn't find name for function 0x77558a9, abstract_origin=0, specification=0x77370f1
  ^C
  $ export PAHOLE_LANG_EXCLUDE=rust
  $ pfunct -F dwarf `pahole --running_kernel_vmlinux` > /dev/null
  $

Later we need to make it also have --lang_exclude and friends to be just
like pahole, maybe even have all this in a common command line parsing
set of routines, for now its enough to make it obey the env var in the
scripts in tests/.

Cc: Alan Maguire <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Stephen Brennan <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

pfunct.c

@@ -43,6 +43,8 @@ static struct conf_load conf_load = {
 	.conf_fprintf = &conf,
 };
 
+static struct languages languages;
+
 struct fn_stats {
 	struct list_head node;
 	struct tag	 *tag;
@@ -533,6 +535,11 @@ static enum load_steal_kind pfunct_stealer(struct cu *cu,
 	return LSK__DELETE;
 }
 
+static struct cu *cu__filter(struct cu *cu)
+{
+	return languages__cu_filtered(&languages, cu, verbose) ? NULL : cu;
+}
+
 /* Name and version of program.  */
 ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
 
@@ -751,6 +758,12 @@ int main(int argc, char *argv[])
                 goto out;
 	}
 
+	if (languages__init(&languages, argv[0]))
+		return rc;
+
+	if (languages.exclude)
+		conf_load.early_cu_filter = cu__filter;
+
 	if (symtab_name != NULL)
 		return elf_symtabs__show(argv + remaining);