Please bump bindgen build dependency

[stintel]

After hitting a segfault I tried enabling the build_bindgen feature, but that didn't work because of a dependency conflict.

$ cargo add paho_mqtt --features build_bindgen
Updating crates.io index
warning: translating paho_mqtt to paho-mqtt
Adding paho-mqtt v0.12.0 to dependencies.
Features:
+ build_bindgen
+ bundled
+ ssl
- vendored-ssl
error: failed to select a version for clang-sys.
... required by package bindgen v0.52.0
... which satisfies dependency bindgen = "^0.52" of package paho-mqtt-sys v0.8.0
... which satisfies dependency paho-mqtt-sys = "^0.8.0" (locked to 0.8.0) of package paho-mqtt v0.12.0
... which satisfies dependency paho-mqtt = "^0.12.0" (locked to 0.12.0) of package auditd-forwarder v0.1.0 (/home/stijn/projects/auditd-forwarder)
versions that meet the requirements ^0.28.0 are: 0.28.1, 0.28.0

the package clang-sys links to the native library clang, but it conflicts with a previous package which links to clang as well:
package clang-sys v1.6.0
... which satisfies dependency clang-sys = "^1" (locked to 1.6.0) of package bindgen v0.64.0
... which satisfies dependency bindgen = ">=0.56" (locked to 0.64.0) of package laurel v0.5.1
... which satisfies dependency laurel = "^0.5.1" (locked to 0.5.1) of package auditd-forwarder v0.1.0 (/home/stijn/projects/auditd-forwarder)
Only one package in the dependency graph may specify the same links value. This helps ensure that only one copy of a native library is linked in the final binary. Try to adjust your dependencies so that only one package uses the links ='clang-sys' value. For more information, see https://doc.rust-lang.org/cargo/reference/resolver.html#links.

failed to select a version for clang-sys which could resolve this conflict

[fpagliughi]

Will do. Yeah, that's pretty old.

[fpagliughi]

I verified the old version was broken for me too, and bumped it to the latest, v0.64. That seems to work for me on Ubuntu 20.04.