[tsan] Inherit TSAN_OPTIONS in allocator_returns_null.cc testcase

[kubamracek]

Summary

This fixes the test on OS X by inheriting the default TSAN_OPTIONS (set in lit.cfg). Namely, we get abort_on_error=0, so the process doesn't crash.

[dvyukov]

LGTM because it can be useful to run tests with custom TSAN_OPTIONS supplied in env.
However, I wonder why do we enable abort_on_error on Mac default (it is not enabled on other OSes), and then disable it as more useful behavior. Won't users also suffer from abort_on_error=1?
I've hit it with Go runtime on Mac. It also lead to a bad behavior and I disabled it for Go on Mac.
Should not we just switch the default to 0?

[samsonov]

I suggest you implement %env_tsan_opts= replacement similar to %env_asan_opts.

[kubamracek]

Superseded by http://reviews.llvm.org/D14698, closing.

test/tsan/allocator_returns_null.cc

 // Test the behavior of malloc/calloc/realloc when the allocation size is huge.
 // By default (allocator_may_return_null=0) the process should crash.
 // With allocator_may_return_null=1 the allocator should return 0.
 //
 // RUN: %clangxx_tsan -O0 %s -o %t
 // RUN: not %run %t malloc 2>&1 | FileCheck %s --check-prefix=CHECK-mCRASH
-// RUN: TSAN_OPTIONS=allocator_may_return_null=0 not %run %t malloc 2>&1 | FileCheck %s --check-prefix=CHECK-mCRASH
-// RUN: TSAN_OPTIONS=allocator_may_return_null=0 not %run %t calloc 2>&1 | FileCheck %s --check-prefix=CHECK-cCRASH
-// RUN: TSAN_OPTIONS=allocator_may_return_null=0 not %run %t calloc-overflow 2>&1 | FileCheck %s --check-prefix=CHECK-coCRASH
-// RUN: TSAN_OPTIONS=allocator_may_return_null=0 not %run %t realloc 2>&1 | FileCheck %s --check-prefix=CHECK-rCRASH
-// RUN: TSAN_OPTIONS=allocator_may_return_null=0 not %run %t realloc-after-malloc 2>&1 | FileCheck %s --check-prefix=CHECK-mrCRASH
+// RUN: TSAN_OPTIONS=$TSAN_OPTIONS:allocator_may_return_null=0 not %run %t malloc 2>&1 | FileCheck %s --check-prefix=CHECK-mCRASH
+// RUN: TSAN_OPTIONS=$TSAN_OPTIONS:allocator_may_return_null=0 not %run %t calloc 2>&1 | FileCheck %s --check-prefix=CHECK-cCRASH
+// RUN: TSAN_OPTIONS=$TSAN_OPTIONS:allocator_may_return_null=0 not %run %t calloc-overflow 2>&1 | FileCheck %s --check-prefix=CHECK-coCRASH
+// RUN: TSAN_OPTIONS=$TSAN_OPTIONS:allocator_may_return_null=0 not %run %t realloc 2>&1 | FileCheck %s --check-prefix=CHECK-rCRASH
+// RUN: TSAN_OPTIONS=$TSAN_OPTIONS:allocator_may_return_null=0 not %run %t realloc-after-malloc 2>&1 | FileCheck %s --check-prefix=CHECK-mrCRASH
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include <assert.h>
 #include <limits>
 int main(int argc, char **argv) {