8286630: [11] avoid -std=c++11 CXX harfbuzz buildflag on Windows

Reviewed-by: mdoerr, clanger

Author: MBaesken

make/lib/Awt2dLibraries.gmk

@@ -542,10 +542,9 @@ ifeq ($(USE_EXTERNAL_HARFBUZZ), true)
 else
   LIBFONTMANAGER_EXTRA_SRC = libharfbuzz
   HARFBUZZ_CFLAGS := -DHAVE_OT -DHAVE_FALLBACK -DHAVE_UCDN -DHAVE_ROUND
-  # Modern HarfBuzz requires c++11.
-  HARFBUZZ_CXXFLAGS := -std=c++11
-
+  # Modern HarfBuzz requires c++11; but VS does not have the flag
   ifneq ($(OPENJDK_TARGET_OS), windows)
+    HARFBUZZ_CXXFLAGS := -std=c++11
     HARFBUZZ_CFLAGS += -DGETPAGESIZE -DHAVE_MPROTECT -DHAVE_PTHREAD \
                        -DHAVE_SYSCONF -DHAVE_SYS_MMAN_H -DHAVE_UNISTD_H \
                        -DHB_NO_PRAGMA_GCC_DIAGNOSTIC