Convert build system to cmake

Also, produce fully static binaries. This means that `gethostname`
does not work (doesn't work with static glibc unless you build it
with `--enable-static-nss`, which no distro builds glibc with).

cpp/core/RocksDBUtils.cpp

@@ -0,0 +1,44 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <rocksdb/env.h>
+#include <rocksdb/merge_operator.h>
+#include <rocksdb/slice.h>
+
+#include "RocksDBUtils.hpp"
+
+namespace { // anonymous namespace
+
+// A 'model' merge operator with int64 addition semantics
+// Implemented as an AssociativeMergeOperator for simplicity and example.
+class Int64AddOperator : public rocksdb::AssociativeMergeOperator {
+ public:
+  bool Merge(const rocksdb::Slice& key, const rocksdb::Slice* existing_value,
+             const rocksdb::Slice& value, std::string* new_value,
+             rocksdb::Logger* logger) const override {
+    int64_t orig_value = 0;
+    if (existing_value) {
+      orig_value = ExternalValue<I64Value>::FromSlice(*existing_value)().i64();
+    }
+    int64_t operand = ExternalValue<I64Value>::FromSlice(value)().i64();
+
+    ALWAYS_ASSERT(new_value);
+    new_value->resize(I64Value::MAX_SIZE);
+    ExternalValue<I64Value>(*new_value)().setI64(orig_value + operand);
+
+    return true;
+  }
+
+  static const char* kClassName() { return "Int64AddOperator"; }
+  static const char* kNickName() { return "int64add"; }
+  const char* Name() const override { return kClassName(); }
+  const char* NickName() const override { return kNickName(); }
+};
+
+}  // anonymous namespace
+
+std::shared_ptr<rocksdb::MergeOperator> CreateInt64AddOperator() {
+  return std::make_shared<Int64AddOperator>();
+}