Yath tests don't forward @INC to system commands

[bbrtj]

bin/dumpenv:

use Data::Dumper;
print Dumper(@INC);

t/env.t:

system($^X, 'bin/dumpenv');
use Data::Dumper; die Dumper(@INC);

prove -l t/env.t --verbose reports:

$VAR1 = 'project/lib';
$VAR2 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0/x86_64-linux';
$VAR3 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0';
$VAR4 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0/x86_64-linux';
$VAR5 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0';
$VAR1 = 'project/lib';
$VAR2 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0/x86_64-linux';
$VAR3 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0';
$VAR4 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0/x86_64-linux';
$VAR5 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0';

yath t/env.t --verbose reports:

( STDOUT )  job  1    $VAR1 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0/x86_64-linux';
( STDOUT )  job  1    $VAR2 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0';
( STDOUT )  job  1    $VAR3 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0/x86_64-linux';
( STDOUT )  job  1    $VAR4 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0';
( STDERR )  job  1    $VAR1 = 'project/lib';
( STDERR )  job  1    $VAR2 = 'project/blib/lib';
( STDERR )  job  1    $VAR3 = 'project/blib/arch';
( STDERR )  job  1    $VAR4 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0/x86_64-linux';
( STDERR )  job  1    $VAR5 = 'perlbrew/perls/perl-5.42.0/lib/site_perl/5.42.0';
( STDERR )  job  1    $VAR6 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0/x86_64-linux';
( STDERR )  job  1    $VAR7 = 'perlbrew/perls/perl-5.42.0/lib/5.42.0';

(path prefixes modified to remove unnecessary details)

I tried changing $ENV and friends before running system, but I can't get project/lib to be added to @INC in the script under yath. This means yath is not seeing my local changes to files in lib and only uses whatever I have installed in perl.