Bug 1492508: Merge upstream patch to pin the ASan DLL. r=ted

The ASan runtime wasn't designed to be unloaded, so pin it in memory.

Differential Revision: https://phabricator.services.mozilla.com/D6943

--HG--
extra : rebase_source : 843fc91b3150f3b264e321ab89bf723a01fc8b3c

build/build-clang/clang-win64.json

@@ -17,6 +17,7 @@
       "workaround-issue38586.patch",
       "r342649-hotpatch-8-byte-nops.patch",
       "r342652-unpoison-thread-stacks.patch",
+      "r343123-pin-asan-dll.patch",
       "loosen-msvc-detection.patch"
     ]
 }

build/build-clang/r343123-pin-asan-dll.patch

@@ -0,0 +1,27 @@
+------------------------------------------------------------------------
+r343123 | dmajor | 2018-09-26 12:28:39 -0400 (Wed, 26 Sep 2018) | 5 lines
+
+[winasan] Pin the ASan DLL to prevent unloading
+
+Differential Revision: https://reviews.llvm.org/D52505
+
+===================================================================
+--- a/compiler-rt/lib/asan/asan_win.cc	(revision 343122)
++++ b/compiler-rt/lib/asan/asan_win.cc	(revision 343123)
+@@ -167,6 +167,14 @@
+ namespace __asan {
+ 
+ void InitializePlatformInterceptors() {
++  // The interceptors were not designed to be removable, so we have to keep this
++  // module alive for the life of the process.
++  HMODULE pinned;
++  CHECK(GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
++                           GET_MODULE_HANDLE_EX_FLAG_PIN,
++                           (LPCWSTR)&InitializePlatformInterceptors,
++                           &pinned));
++
+   ASAN_INTERCEPT_FUNC(CreateThread);
+   ASAN_INTERCEPT_FUNC(SetUnhandledExceptionFilter);
+   CHECK(::__interception::OverrideFunction("NtTerminateThread",
+
+------------------------------------------------------------------------