[C-libcurl] Add object.c to CMakeLists to compile

Created by: ityuhui

After the C client library is generated, I try to link it to my program.

gcc main.c -g -I../../c_k8s_api_client/include -I../../c_k8s_api_client/model -I../../c_k8s_api_client/api -L../../c_k8s_api_client/build -lkubernetes -lpthread -lssl -lz -lcurl -o lsecretOutCluster

But there are some link errors:

../../c_k8s_api_client/build/libk8s.a(CoreV1API.c.o): In function `CoreV1API_patchCoreV1Namespace':
/root/c_k8s_api_client/api/CoreV1API.c:19072: undefined reference to `object_convertToJSON'
../../c_k8s_api_client/build/libk8s.a(CoreV1API.c.o): In function `CoreV1API_patchCoreV1NamespaceStatus':
/root/c_k8s_api_client/api/CoreV1API.c:19219: undefined reference to `object_convertToJSON'
...

The reason is : The source code file "object.c" is not compiled into the C client library (libkubernetes).

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