Implement buildFileTable interface

The buildFileTable interface will be used by the ReadFileIntoMemory
and WriteFileFromMemory commands to get the file table and map the
file handle to the file path.

Change-Id: Ibdc01737d8925ef918c4fbe2919108d96a2807ab
Signed-off-by: Tom Joseph <tomjoseph@in.ibm.com>
diff --git a/libpldmresponder/file_table.cpp b/libpldmresponder/file_table.cpp
index 85f417c..9264f21 100644
--- a/libpldmresponder/file_table.cpp
+++ b/libpldmresponder/file_table.cpp
@@ -115,5 +115,15 @@
     return table;
 }
 
+FileTable& buildFileTable(const std::string& fileTablePath)
+{
+    static FileTable table;
+    if (table.isEmpty())
+    {
+        table = std::move(FileTable(fileTablePath));
+    }
+    return table;
+}
+
 } // namespace filetable
 } // namespace pldm