Add back UTF-32 for now and fix a MSVC build issue

patches/vscomp.patch

Index: patches/vscomp.patch
diff --git a/patches/vscomp.patch b/patches/vscomp.patch
index 22bbba4234ceda905531bb18c55e0e719976895a..de079f059876f839251ba78b0a27b96db884d57d 100644
--- a/patches/vscomp.patch
+++ b/patches/vscomp.patch
@@ -50,3 +50,16 @@ index e99670d..c9a3502 100644
      char type[256];
      Calendar::getCalendarTypeFromLocale(fLoc, type, UPRV_LENGTHOF(type), status);
      if (U_FAILURE(status)) {
+diff --git a/source/common/sharedobject.h b/source/common/sharedobject.h
+index 4402869..e5062cc 100644
+--- a/source/common/sharedobject.h
++++ b/source/common/sharedobject.h
+@@ -21,7 +21,7 @@ U_NAMESPACE_BEGIN
+  * update cache metrics. No other part of ICU, except for SharedObject,
+  * should directly call the methods of this base class.
+  */
+-class UnifiedCacheBase : public UObject {
++class U_COMMON_API UnifiedCacheBase : public UObject {
+ public:
+     UnifiedCacheBase() { }
+