Fix building without curl

[gkozar]

WITH_OAUTHBEARER_OIDC is always defined, but it set to 0 if disabled, and 1 if enabled.
This is because packaging/cmake/config.h.in has: #cmakedefine01 WITH_OAUTHBEARER_OIDC

Therefore, #ifdef WITH_OAUTHBEARER_OIDC always runs.

[confluent-cla-assistant]

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[gkozar]

Closing because it's a duplicate of #5230