server: Compile json object generation source separately

Declare entry points in a dedicated header and compile the source
separately instead of including it in the server implementation.

Source/cmJsonObjects.h

@@ -0,0 +1,27 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#ifndef cmJsonObjects_h
+#define cmJsonObjects_h
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include "cm_jsoncpp_value.h"
+
+#include <string>
+#include <vector>
+
+class cmake;
+class cmGlobalGenerator;
+
+extern void cmGetCMakeInputs(const cmGlobalGenerator* gg,
+                             const std::string& sourceDir,
+                             const std::string& buildDir,
+                             std::vector<std::string>* internalFiles,
+                             std::vector<std::string>* explicitFiles,
+                             std::vector<std::string>* tmpFiles);
+
+extern Json::Value cmDumpCodeModel(const cmake* cm);
+extern Json::Value cmDumpCTestInfo(const cmake* cm);
+extern Json::Value cmDumpCMakeInputs(const cmake* cm);
+
+#endif