fix(build): don't require plugin_abi.h to be formatted

Signed-off-by: Grzegorz Nosek <grzegorz.nosek@sysdig.com>

Author: gnosek

.clang-format-ignore

@@ -14,3 +14,5 @@ driver/syscall_compat_s390x.h
 driver/syscall_compat_x86_64.h
 driver/syscall_ia32_64_map.c
 driver/syscall_table.c
+# The autogenerated plugin ABI header is not formatted
+userspace/plugin/plugin_abi.h