This works for me as in it starts building and doesn't die immediately with CreateProcess(NULL, better than renaming sh.exe and make.exe :)

Alien-wxWidgets-0.69\inc\My\Build\Win32.pm

sub build_wxwidgets {
    my $self = shift;
    my $old_dir = Cwd::cwd();

    my $uni = $self->awx_unicode ? 'UNICODE=1'   : 'UNICODE=0';
    my $mslu = $self->awx_mslu   ? 'MSLU=1'      : 'MSLU=0';
    my $dbg = $self->awx_debug   ? 'BUILD=debug' : 'BUILD=release';
    my $opt = join ' ', $uni, $mslu, $dbg, 'SHARED=1', 'SHELL=cmd.exe'
+;
[download]

This was a flop , dies with CreateProcess(NULL, probably all that reboot talk ... nonsense :)

Alien-wxWidgets-0.69\inc\My\Build\Win32.pm
sub massage_environment {
    my( $self ) = shift;

    if( $self->notes( 'build_wx' ) ) {
        $ENV{WXWIN} = $ENV{WXDIR} = File::Spec->rel2abs
          ( $self->notes( 'build_data' )->{data}{directory} );
        $ENV{SHELL} = 'cmd.exe' if $Config::Config{sh}=~/cmd/i;
        
        my $mingw_gcc = My::Build::Base->awx_path_search( '*-gcc-*.exe
+' ); # i686-w64-mingw32-gcc-4.6.3.exe
        my $basename = File::Basename::basename($mingw_gcc, '.exe' );
        $basename = "libexec/gcc/$1/$2" if $basename =~ m{^(.+?)-gcc-(
+.+)}is;
        my $new_path = File::Spec->rel2abs(
            File::Spec->catfile(
                File::Basename::dirname($mingw_gcc) ,
                File::Spec->updir, 
                $basename
            )
        );
#~         die "SHELL=$ENV{SHELL}\n$mingw_gcc\n$basename\n$new_path";
        $ENV{PATH}.=';'.$new_path;
## didnt work

    }
}
[download]