Cannot match an empty line

[espindola]

I am trying to use lit with a file format that uses empty line for delimiters, but it doesn't seem to be possible to match those. A reduced example is

# RUN: sh @file

# CHECK: line1
# CHECK: [[^$]]
# CHECK: line2

echo line1
echo
echo line2

With llvm's FileCheck it is possible to use {{^$}}.