Operator @rx has different flags in two engines

[airween]

Describe the bug

It seems like the @rx operator has a different behavior in two engines (mod_security2 and libmodsecurity3)

mod_security2 has these PCRE flags:

PCRE2, PCRE

libmodsecurity3 has these ones:

PCRE2, PCRE

To Reproduce

coreruleset/coreruleset#3277

We should discuss:

• do we want to resolve this issue?
• how?

[airween]

I think this is a good idea, I mean add a build flag to libmodsecurity3 (mod_security2 is not affected) which changes the flag, and not in the next release but after that we make it mandatory (and we can add an optional build flag to keep the old (current) one).

[marcstern]

PCRE2_DOTALL & PCRE2_DOLLAR_ENDONLY look the right way for me as we need to check multiline ARGS