8283323: libharfbuzz optimization level results in extreme build times

Reviewed-by: mdoerr
Backport-of: 2c43ecb43fa3c94b69478039f1cd70ed4a577768

make/lib/Awt2dLibraries.gmk

@@ -577,7 +577,6 @@ else
 
 endif
 
-
 LIBFONTMANAGER_EXTRA_HEADER_DIRS := \
     libharfbuzz \
     libharfbuzz/hb-ucdn \
@@ -593,6 +592,14 @@ BUILD_LIBFONTMANAGER_FONTLIB +=  $(LIBFREETYPE_LIBS)
 
 LIBFONTMANAGER_OPTIMIZATION := HIGHEST
 
+ifneq ($(filter $(TOOLCHAIN_TYPE), gcc clang), )
+  # gcc (and to an extent clang) is particularly bad at optimizing these files,
+  # causing a massive spike in compile time. We don't care about these
+  # particular files anyway, so lower optimization level.
+  BUILD_LIBFONTMANAGER_hb-subset.cc_OPTIMIZATION := SIZE
+  BUILD_LIBFONTMANAGER_hb-subset-plan.cc_OPTIMIZATION := SIZE
+endif
+
 ifeq ($(OPENJDK_TARGET_OS), windows)
   LIBFONTMANAGER_EXCLUDE_FILES += X11FontScaler.c \
       X11TextRenderer.c