t/deploy.t and t/revert.t fail on some systems

[eserte]

The test suite fails on my freebsd smokers:

Warnings from executed actions/002/verify: exec failed: No such file or directory at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.
exec failed: No such file or directory at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.
 at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.

# Tests were run but no plan was declared and done_testing() was not seen.
# Looks like your test exited with 1 just after 4.
t/deploy.t ............... 
Dubious, test returned 1 (wstat 256, 0x100)
All 4 subtests passed 
...
Warnings from executed actions/005/deploy: exec failed: No such file or directory at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.
Warnings from executed actions/005/verify: exec failed: No such file or directory at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.
exec failed: No such file or directory at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.
 at /usr/home/cpansand/.cpan/build/2019100304/App-Dest-1.25-3/blib/lib/App/Dest.pm line 707.

# Tests were run but no plan was declared and done_testing() was not seen.
# Looks like your test exited with 1 just after 3.
t/revert.t ............... 
Dubious, test returned 1 (wstat 256, 0x100)
All 3 subtests passed 

The problem seems to be that the wrapper scripts are using /bin/bash. There's no guarantee on non-linux systems that bash is installed (and I think that on some minimal linux distributions there's no bash either). And if bash is installed on *BSD systems, then it's located in /usr/local/bin, as it's 3rd party software. Probably it's better to use /bin/sh instead.