[tlbuild] texk/web2c/omegafonts/check.test: Inconsistent behaviour

[Johannes Hielscher]

> error (attached: excerpt from texk/web2c/omegafonts/test-suite.log).
-------------- next part --------------
A non-text attachment was scrubbed...
Name: omegafonts-check.test_from_Build_test-suite
Type: application/octet-stream
Size: 899 bytes
Desc: not available
URL: <http://tug.org/pipermail/tlbuild/attachments/20180408/7f658276/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: omegafonts-check.test_from_shell
Type: application/octet-stream
Size: 2461 bytes
Desc: not available
URL: <http://tug.org/pipermail/tlbuild/attachments/20180408/7f658276/attachment-0001.obj>