tools/automake: control all cleaning with clean variables

Automake previously makes rules for the target maintainer-clean
to remove both the contents of MAINTAINERCLEANFILES and BUILT_SOURCES.

In order to have finer control over what is removed,
let there only be a rule for deleting MAINTAINERCLEANFILES,
and set MAINTAINERCLEANFILES to a default value of BUILT_SOURCES
if only conditional or missing, and append BUILT_SOURCES if user-defined.

In order to maintain conditional values for MAINTAINERCLEANFILES
while keeping a default value, change the behavior of automake
to output unconditional definitions before conditions.

Signed-off-by: Michael Pratt <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16522
Signed-off-by: Robert Marko <[email protected]>

tools/automake/patches/300-output-TRUE-cond-first.patch

@@ -0,0 +1,34 @@
+--- a/lib/Automake/Variable.pm
++++ b/lib/Automake/Variable.pm
+@@ -1259,8 +1259,15 @@ sub output_variables ()
+   foreach my $var (@vars)
+     {
+       my $v = rvar $var;
++      # Output unconditional definitions before conditional ones.
++      if ($v->def (TRUE)) {
++	  $res .= $v->output (TRUE)
++	    if $v->rdef (TRUE)->owner == VAR_AUTOMAKE;
++      }
+       foreach my $cond ($v->conditions->conds)
+ 	{
++	  # TRUE is handled already.
++	  next if $cond->string eq "TRUE";
+ 	  $res .= $v->output ($cond)
+ 	    if $v->rdef ($cond)->owner == VAR_AUTOMAKE;
+ 	}
+@@ -1270,8 +1277,15 @@ sub output_variables ()
+   foreach my $var (@vars)
+     {
+       my $v = rvar $var;
++      # Output unconditional definitions before conditional ones.
++      if ($v->def (TRUE)) {
++	  $res .= $v->output (TRUE)
++	    if $v->rdef (TRUE)->owner != VAR_AUTOMAKE;
++      }
+       foreach my $cond ($v->conditions->conds)
+ 	{
++	  # TRUE is handled already.
++	  next if $cond->string eq "TRUE";
+ 	  $res .= $v->output ($cond)
+ 	    if $v->rdef ($cond)->owner != VAR_AUTOMAKE;
+ 	}

tools/automake/patches/310-maintainer-clean-built_sources.patch

@@ -0,0 +1,49 @@
+--- a/bin/automake.in
++++ b/bin/automake.in
+@@ -4745,12 +4745,42 @@ sub handle_clean
+     if var ('CLEANFILES');
+   $clean_files{'$(DISTCLEANFILES)'} = DIST_CLEAN
+     if var ('DISTCLEANFILES');
+-  $clean_files{'$(MAINTAINERCLEANFILES)'} = MAINTAINER_CLEAN
+-    if var ('MAINTAINERCLEANFILES');
+ 
+   # Built sources are automatically removed by maintainer-clean.
+-  $clean_files{'$(BUILT_SOURCES)'} = MAINTAINER_CLEAN
+-    if var ('BUILT_SOURCES');
++  # For each defined condition of the maintainer-clean variable, append built sources
++  # and create an unconditional definition with built sources if not already defined.
++  # Then, for each definition of built sources without maintainer-clean defined, define it.
++  # Otherwise, if the variable is not user-defined, define it with built sources.
++  my $mcleanvar = var ('MAINTAINERCLEANFILES');
++  if ($mcleanvar) {
++    foreach my $rcond ($mcleanvar->conditions->conds)
++    {
++      if (! grep { $_ eq '$(BUILT_SOURCES)' } $mcleanvar->value_as_list ($rcond)) {
++	Automake::Variable::define ($mcleanvar->name, VAR_MAKEFILE, '+', $rcond,
++				    '$(BUILT_SOURCES)', '', INTERNAL, VAR_ASIS)
++	  if vardef ('BUILT_SOURCES', $rcond);
++      }
++    }
++    my $bsources = var ('BUILT_SOURCES');
++    if ($bsources) {
++      foreach my $rcond ($bsources->conditions->conds)
++      {
++	Automake::Variable::define ($mcleanvar->name, VAR_MAKEFILE, '', $rcond,
++				    '$(BUILT_SOURCES)', '', INTERNAL, VAR_ASIS)
++	  if ! vardef ($mcleanvar, $rcond);
++      }
++      if (! vardef ($mcleanvar, TRUE)) {
++	Automake::Variable::define ($mcleanvar->name, VAR_MAKEFILE, '', TRUE,
++				    '$(BUILT_SOURCES)', '', INTERNAL, VAR_ASIS);
++      }
++    }
++  } else {
++    Automake::Variable::define ('MAINTAINERCLEANFILES', VAR_MAKEFILE, '', TRUE,
++				'$(BUILT_SOURCES)', '', INTERNAL, VAR_ASIS)
++      if var ('BUILT_SOURCES');
++  }
++  $clean_files{'$(MAINTAINERCLEANFILES)'} = MAINTAINER_CLEAN
++    if var ('MAINTAINERCLEANFILES');
+ 
+   # Compute a list of "rm"s to run for each target.
+   my %rms = (MOSTLY_CLEAN, [],