This is very much a hack that ought to only mask out a gcc build.

--- a/make/lib/Awt2dLibraries.gmk	Wed Apr 12 13:26:01 2023
+++ b/make/lib/Awt2dLibraries.gmk	Thu Apr  6 08:06:02 2023
@@ -68,7 +68,7 @@
 
 ################################################################################
 
-ifeq ($(call And, $(call isTargetOs, solaris) $(call isTargetCpuArch, sparc)), true)
+ifeq ($(call And, $(call isTargetOs, not-solaris) $(call isTargetCpuArch, sparc)), true)
 
   # libmlib_image_v is basically built from mlib_image sources, with some additions
   # and some exclusions.
@@ -127,7 +127,7 @@
     $(TOPDIR)/src/$(MODULE)/$(OPENJDK_TARGET_OS_TYPE)/native/common/awt \
     #
 
-ifeq ($(call And, $(call isTargetOs, solaris) $(call isTargetCpuArch, sparc)), true)
+ifeq ($(call And, $(call isTargetOs, not-really-solaris) $(call isTargetCpuArch, sparc)), true)
   LIBAWT_EXTRA_SRC += $(TOPDIR)/src/$(MODULE)/share/native/common/awt/medialib
 endif
 
@@ -155,7 +155,7 @@
       #
 endif
 
-ifeq ($(call And, $(call isTargetOs, solaris) $(call isTargetCpu, sparcv9)), true)
+ifeq ($(call And, $(call isTargetOs, not-really-solaris) $(call isTargetCpu, sparcv9)), true)
   LIBAWT_EXFILES += java2d/loops/MapAccelFunc.c
 else
   LIBAWT_EXCLUDES += \
@@ -182,7 +182,7 @@
 
 LIBAWT_CFLAGS += -D__MEDIALIB_OLD_NAMES -D__USE_J2D_NAMES $(X_CFLAGS)
 
-ifeq ($(call And, $(call isTargetOs, solaris) $(call isTargetCpu, sparcv9)), true)
+ifeq ($(call And, $(call isTargetOs, not-really-solaris) $(call isTargetCpu, sparcv9)), true)
   LIBAWT_CFLAGS += -xarch=sparcvis -DMLIB_ADD_SUFF \
       $(TOPDIR)/src/$(MODULE)/unix/native/libmlib_image/vis_$(OPENJDK_TARGET_CPU_BITS).il
 
@@ -189,7 +189,7 @@
   LIBAWT_ASFLAGS = -P -xarch=v9a
 endif
 
-ifeq ($(call isTargetOs, solaris), false)
+ifeq ($(call isTargetOs, not-really-solaris), false)
   LIBAWT_CFLAGS += -DMLIB_NO_LIBSUNMATH
 endif