[sanitizer] Get full argv and envp on glibc.
[sanitizer] Get full argv and envp on glibc.

/proc/$PID/cmdline is clipped to 4Kb.
Locate argv and envp on the main thread stack.


git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@175163 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt