Offer alternative for cxxabi on Windows (Swift+Clang).

* This fixes the clang compilation of OpenTimelineIO on Windows, when compiling with Swift.

src/opentimelineio/stringUtils.cpp

@@ -4,7 +4,12 @@
 #include "opentimelineio/serializableObject.h"
 #if defined(__GNUC__) || defined(__clang__)
 #    include <cstdlib>
-#    include <cxxabi.h>
+#    if __has_include(<cxxabi.h>)
+#       define OTIO_HAVE_DEMANGLER 1
+#       include <cxxabi.h>
+#    else // !__has_include(<cxxabi.h>)
+#        define OTIO_HAVE_DEMANGLER 0
+#    endif // __has_include(<cxxabi.h>)
 #    include <memory>
 #else
 #    include <typeinfo>
@@ -15,6 +20,7 @@ namespace {
 std::string
 cxxabi_type_name_for_error_mesage(const char* name)
 {
+    #if OTIO_HAVE_DEMANGLE
     int status = -4; // some arbitrary value to eliminate the compiler warning
 
     std::unique_ptr<char, void (*)(void*)> res{
@@ -23,6 +29,9 @@ cxxabi_type_name_for_error_mesage(const char* name)
     };
 
     return (status == 0) ? res.get() : name;
+    #else // !OTIO_HAVE_DEMANGLE
+    return name;
+    #endif // OTIO_HAVE_DEMANGLE
 }
 #endif
 } // namespace