Add existing dynamorio-based external tools for value profilers

[JerryYouxin]

We develop a portable and efficient framework VClinic for fine-grained value profilers built atop DynamoRIO. We wish to add a short line of intrudocution with corresponding external link into the README.

In short, the highlights of VClinic built upon DynamoRIO are shown as follows:

• Decoupling implementation of value tracing and value profiling
• Implement trace buffer with lightweight inline assembly for efficient value tracing
• Support operand-centric view for development of fine-grained value profilers instead of instruction-centric view of DynamoRIO.
• Currently support both ARM and X86 platforms. In the future, it can support all DynamoRIO-supported architectures.

The detailed document of VClinic can be referred to here and the related technical paper

[derekbruening]

Thank you for reaching out. Happy to add a link.

[derekbruening]

The x64 failure is a known flake we have not been able to reproduce well enough to fix: Invalid trace entry type thread_exit (23) before a bundle #4167.