[BUG] `-DHAVE_GNUTLS` missing when `have_gnutls` is enabled

[Lihis]

Prerequisites

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Description

-DHAVE_GNUTLS is not defined even though gnutls/gnutls.h is found.

Steps to Reproduce

1. Install GnuTLS development package
2. Run configure
3. Run build

Expected behavior: -DHAVE_GNUTLS is in compiler flags

Actual behavior: -DHAVE_GNUTLS is not in compiler flags

Reproduces how often: 100%

Versions

• Affects versions since 000979b