clang update.py: When running tests on Windows, make sure DIA works.

tools/clang/scripts/update.py

Index: tools/clang/scripts/update.py
diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index 0abb42af0586bd7085e805720d9d15c2fec5a2c2..e5b75942e56e04099a681dfee1926bfcfa051265 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -351,6 +351,13 @@ def GetVSVersion():
   return vs_version
 
 
+def CopyDiaDllTo(target_dir):
+  # This script always wants to use the 64-bit msdia*.dll.
+  dia_path = os.path.join(GetVSVersion().Path(), 'DIA SDK', 'bin', 'amd64')
+  dia_dll = os.path.join(dia_path, 'msdia140.dll')  # Bump after VC updates.
+  CopyFile(dia_dll, target_dir)
+
+
 def UpdateClang(args):
   print 'Updating Clang to %s...' % PACKAGE_VERSION
 
@@ -384,6 +391,8 @@ def UpdateClang(args):
     try:
       DownloadAndUnpack(cds_full_url, LLVM_BUILD_DIR)
       print 'clang %s unpacked' % PACKAGE_VERSION
+      if sys.platform == 'win32':
+        CopyDiaDllTo(os.path.join(LLVM_BUILD_DIR, 'bin'))
       # Download the gold plugin if requested to by an environment variable.
       # This is used by the CFI ClusterFuzz bot, and it's required for official
       # builds on linux.
@@ -476,6 +485,8 @@ def UpdateClang(args):
     RunCommand(['cmake'] + bootstrap_args + [LLVM_DIR], msvc_arch='x64')
     RunCommand(['ninja'], msvc_arch='x64')
     if args.run_tests:
+      if sys.platform == 'win32':
+        CopyDiaDllTo(os.path.join(LLVM_BOOTSTRAP_DIR, 'bin'))
       RunCommand(['ninja', 'check-all'], msvc_arch='x64')
     RunCommand(['ninja', 'install'], msvc_arch='x64')
     if args.gcc_toolchain:
@@ -760,6 +771,8 @@ def UpdateClang(args):
     os.chdir(LLVM_BUILD_DIR)
     RunCommand(['ninja', 'cr-check-all'], msvc_arch='x64')
   if args.run_tests:
+    if sys.platform == 'win32':
+      CopyDiaDllTo(os.path.join(LLVM_BUILD_DIR, 'bin'))
     os.chdir(LLVM_BUILD_DIR)
     RunCommand(['ninja', 'check-all'], msvc_arch='x64')