[compiler-rt] Fix interception of multiple defined symbols.

Summary:
The MSVC compiler is generating multiple instance of the exception handler
when compiling on win64 with /MD.

see: https://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx

Two tests were failing when running:
```
ninja check-asan-dynamic.
```

The tests were failing because only the first occurence of the function was patched.
The function `__C_specific_handler` is defined in `ntdll` and `vcruntime140`.

After this patch, there is still two remaining tests failing.
```
********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 87.81s
********************
Failing Tests (2):
    AddressSanitizer-x86_64-windows-dynamic :: TestCases/Windows/dll_intercept_memchr.cc
    AddressSanitizer-x86_64-windows-dynamic :: TestCases/Windows/dll_intercept_memcpy_indirect.cc

  Expected Passes    : 342
  Passes With Retry  : 2
  Expected Failures  : 16
  Unsupported Tests  : 152
  Unexpected Failures: 2
```

Reviewers: rnk, vitalybuka

Subscribers: vitalybuka, llvm-commits, chrisha, dberris

Differential Revision: https://reviews.llvm.org/D24983

llvm-svn: 282614

Author: bergeret

compiler-rt/lib/interception/interception_win.cc

@@ -915,19 +915,18 @@ uptr InternalGetProcAddress(void *module, const char *func_name) {
   return 0;
 }
 
-static bool GetFunctionAddressInDLLs(const char *func_name, uptr *func_addr) {
-  *func_addr = 0;
+bool OverrideFunction(
+    const char *func_name, uptr new_func, uptr *orig_old_func) {
+  bool hooked = false;
   void **DLLs = InterestingDLLsAvailable();
-  for (size_t i = 0; *func_addr == 0 && DLLs[i]; ++i)
-    *func_addr = InternalGetProcAddress(DLLs[i], func_name);
-  return (*func_addr != 0);
-}
-
-bool OverrideFunction(const char *name, uptr new_func, uptr *orig_old_func) {
-  uptr orig_func;
-  if (!GetFunctionAddressInDLLs(name, &orig_func))
-    return false;
-  return OverrideFunction(orig_func, new_func, orig_old_func);
+  for (size_t i = 0; DLLs[i]; ++i) {
+    uptr func_addr = InternalGetProcAddress(DLLs[i], func_name);
+    if (func_addr &&
+        OverrideFunction(func_addr, new_func, orig_old_func)) {
+      hooked = true;
+    }
+  }
+  return hooked;
 }
 
 bool OverrideImportedFunction(const char *module_to_patch,