[lldb] Allow building using Mingw-w64 on Windows. (llvm#150398)

I wasn't able to build lldb using Mingw-w64 on Windows without changing
these 3 lines. It seems like `std::atomic<bool>` wasn't being found
without `#include <atomic>` and `ceil` was defaulting to `std::ceil`
instead of `std::chrono::ceil`, but I'm not smart enough to know the
root cause. I'm sure I'm not the first people to try and compile lldb
(and clang and lld) with Mingw-w64 and I don't know if something is
wrong with my Mingw-w64, but my changes shouldn't have any affect if
they aren't needed.

Author: cvspvr

lldb/source/Host/windows/MainLoopWindows.cpp

@@ -14,6 +14,7 @@
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/WindowsError.h"
 #include <algorithm>
+#include <atomic>
 #include <cassert>
 #include <ctime>
 #include <io.h>

lldb/source/Host/windows/PipeWindows.cpp

@@ -279,7 +279,8 @@ llvm::Expected<size_t> PipeWindows::Read(void *buf, size_t size,
     return Status(failure_error, eErrorTypeWin32).takeError();
 
   DWORD timeout_msec =
-      timeout ? ceil<std::chrono::milliseconds>(*timeout).count() : INFINITE;
+      timeout ? std::chrono::ceil<std::chrono::milliseconds>(*timeout).count()
+              : INFINITE;
   DWORD wait_result =
       ::WaitForSingleObject(m_read_overlapped.hEvent, timeout_msec);
   if (wait_result != WAIT_OBJECT_0) {
@@ -324,7 +325,8 @@ llvm::Expected<size_t> PipeWindows::Write(const void *buf, size_t size,
     return Status(failure_error, eErrorTypeWin32).takeError();
 
   DWORD timeout_msec =
-      timeout ? ceil<std::chrono::milliseconds>(*timeout).count() : INFINITE;
+      timeout ? std::chrono::ceil<std::chrono::milliseconds>(*timeout).count()
+              : INFINITE;
   DWORD wait_result =
       ::WaitForSingleObject(m_write_overlapped.hEvent, timeout_msec);
   if (wait_result != WAIT_OBJECT_0) {