linux: add kernelPreferBuiltin platform option

This allows to use kernelAutoModules but still compile in any options that are set so in template config.
It's helpful for ARM and maybe other platforms where defaul configurations are useful because they compile in
modules that we and udev cannot autodetect now.

pkgs/os-specific/linux/kernel/generate-config.pl

@@ -17,6 +17,7 @@ my $wd = getcwd;
 
 my $debug = $ENV{'DEBUG'};
 my $autoModules = $ENV{'AUTO_MODULES'};
+my $preferBuiltin = $ENV{'PREFER_BUILTIN'};
     
 $SIG{PIPE} = 'IGNORE';
 
@@ -73,7 +74,7 @@ sub runConfig {
                 my $question = $1; my $name = $2; my $alts = $3;
                 my $answer = "";
                 # Build everything as a module if possible.
-                $answer = "m" if $autoModules && $alts =~ /\/m/;
+                $answer = "m" if $autoModules && $alts =~ /\/m/ && !($preferBuiltin && $alts =~ /Y/);
                 $answer = $answers{$name} if defined $answers{$name};
                 print STDERR "QUESTION: $question, NAME: $name, ALTS: $alts, ANSWER: $answer\n" if $debug;
                 print OUT "$answer\n";