[compiler-rt][asan] Fix incorrect macro preventing ICF with MSVC

Summary:
The DLL thunks are stubs added to an instrumented DLL to redirect ASAN API calls
to the real ones in the main executable. These thunks must contain dummy
code before __asan_init got called. Unfortunately, MSVC linker is doing ICF and is
merging functions with the same body.


In our case, this two ASAN thunks were incorrectly merged:
```
asan_interface.inc:16
INTERFACE_FUNCTION(__asan_before_dynamic_init)
```
```
sanitizer_common_interface.inc:16
INTERFACE_FUNCTION(__sanitizer_verify_contiguous_container)
```

The same thunk got patched twice. After the second patching, calls to
`__asan_before_dynamic_init` are redirected to `__sanitizer_verify_contiguous_container`
and trigger a DCHECK on incorrect operands/

The problem was caused by the macro that is only using __LINE__ to prevent
collapsing code.
```
 #define INTERCEPT_SANITIZER_FUNCTION(name)
   extern "C" __declspec(noinline) void name() {
   volatile int prevent_icf = (__LINE__ << 8); (void)prevent_icf;
```

The current patch is adding __COUNTER__ which is safer than __LINE__.

Also, to precent ICF (guarantee that code is different), we are using a unique attribute:
  - the name of the function

Reviewers: rnk

Reviewed By: rnk

Subscribers: llvm-commits, kubamracek, chrisha, dberris

Differential Revision: https://reviews.llvm.org/D30219

llvm-svn: 295761