scudo: Update TLS_SLOT_SANITIZER value.

Android now allocates only 8 fixed TLS slots. Somehow we were getting away
with using a non-existent slot until now, but in some cases the TLS slots
were being placed at the end of a page, which led to a segfault at startup.

Differential Revision: https://reviews.llvm.org/D69191

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@375276 91177308-0d34-0410-b5e6-96231b3b80d8

Author: pcc

lib/scudo/standalone/linux.h

@@ -55,7 +55,7 @@ struct MapPlatformData {};
 // The Android Bionic team has allocated a TLS slot for sanitizers starting
 // with Q, given that Android currently doesn't support ELF TLS. It is used to
 // store sanitizer thread specific data.
-static const int TLS_SLOT_SANITIZER = 8; // TODO(kostyak): 6 for Q!!
+static const int TLS_SLOT_SANITIZER = 6;
 
 ALWAYS_INLINE uptr *getAndroidTlsPtr() {
   return reinterpret_cast<uptr *>(&__get_tls()[TLS_SLOT_SANITIZER]);