Fix compilation errors from CppCheck fixes

- Add missing #include <string> to symbols_linux.cpp
- Revert alloca() replacement in flightRecorder.cpp - Buffer class
  requires flexible array allocation that alloca() provides
- Keep cppcheck suppression to acknowledge the warning

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jbachorik

ddprof-lib/src/main/cpp/flightRecorder.cpp

@@ -1612,8 +1612,8 @@ void FlightRecorder::recordLog(LogLevel level, const char *message,
 
   if (len > MAX_STRING_LENGTH)
     len = MAX_STRING_LENGTH;
-  std::vector<char> buf_storage(len + 40);
-  Buffer *buf = reinterpret_cast<Buffer *>(buf_storage.data());
+  // cppcheck-suppress obsoleteFunctions
+  Buffer *buf = (Buffer *)alloca(len + 40);
   buf->reset();
 
   int start = buf->skip(5);

ddprof-lib/src/main/cpp/symbols_linux.cpp

@@ -25,6 +25,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <string>
 #include <unordered_map>
 #include <unordered_set>