Test: test: compat: support various platforms and slow CI * can't assume number of null bytes in gzip result i.e. number of null byte-terminated log messages produced by this test * can't use echo -n … in OS X / Darwin -- use printf instead * protect against inappropriate failure on slow machine

Test: test: compat: support various platforms and slow CI * can't assume number of null bytes in gzip result i.e. number of null byte-terminated log messages produced by this test * can't use echo -n … in OS X / Darwin -- use printf instead * protect against inappropriate failure on slow machine #69