fix on ReExec implementation for tsan under linux_arm environment

[OldChicken1]

Currently under linux arm platform, if ASLR is enabled, executable that is compiled and linked with tsan options will be set a maximum stack size instead of unlimited, and get reexecuted (because of a aarch patch, see details https://reviews.llvm.org/D18003) . And that will rename the process as exe. If multiple process run with tsan, then they will all be renamed as exe and the tsan reports are also named as exe.{pid}, which makes it hard to identify a specific process. So instead of executing the link to the executable("/proc/self/exe"), try to pass the original argv[0] to execve function. And this will make the process reexecuted with their original name.

[MLopez-Ibanez]

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[jwakely]

This should be fixed upstream in LLVM, then GCC will pick it up from there. A pull request here won't achieve anything.

It seems to me that using readlink to resolve /proc/self/exe would be better. The argv[0] value might not be a valid pathname and so trying to re-execute it would fail.