Expose build info (#7399)

include/xgboost/c_api.h

@@ -42,6 +42,15 @@ typedef void *BoosterHandle;  // NOLINT(*)
  */
 XGB_DLL void XGBoostVersion(int* major, int* minor, int* patch);
 
+/*!
+ * \brief Get compile information of shared library.
+ *
+ * \param out string encoded JSON object containing build flags and dependency version.
+ *
+ * \return 0 for success, -1 for failure
+ */
+XGB_DLL int XGBBuildInfo(char const **out);
+
 /*!
  * \brief get string message of the last error
  *