[sanitizer][NFC] Fix compilation error on Windows

And remove unnecessary const_cast in ubsan.

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -605,6 +605,7 @@ class InternalScopedString {
   }
   void append(const char *format, ...);
   const char *data() const { return buffer_.data(); }
+  char *data() { return buffer_.data(); }
 
  private:
   InternalMmapVector<char> buffer_;

compiler-rt/lib/ubsan/ubsan_monitor.cpp

@@ -54,7 +54,7 @@ void __ubsan::__ubsan_get_current_report_data(const char **OutIssueKind,
   // lowercase letter.
   char FirstChar = *Buf.data();
   if (FirstChar >= 'a' && FirstChar <= 'z')
-    *const_cast<char *>(Buf.data()) += 'A' - 'a';
+    *Buf.data() += 'A' - 'a';
 
   *OutIssueKind = CurrentUBR->IssueKind;
   *OutMessage = Buf.data();