drm/amd/display: Support clang option for stack alignment

As previously fixed for dml in commit 4769278e ("amdgpu/dc/dml:
Support clang option for stack alignment") and calcs in commit
cc32ad8f ("amdgpu/dc/calcs: Support clang option for stack
alignment"), dcn20 uses an option that is not available with clang:

clang: error: unknown argument: '-mpreferred-stack-boundary=4'
scripts/Makefile.build:281: recipe for target 'drivers/gpu/drm/amd/amdgpu/../display/dc/dcn20/dcn20_resource.o' failed

Use the same trick that we have in the other two files.

Fixes: 7ed4e635 ("drm/amd/display: Add DCN2 HW Sequencer and Resource")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/Makefile

@@ -10,7 +10,13 @@ ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
 DCN20 += dcn20_dsc.o
 endif
 
-CFLAGS_dcn20_resource.o := -mhard-float -msse -mpreferred-stack-boundary=4
+ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
+	cc_stack_align := -mpreferred-stack-boundary=4
+else ifneq ($(call cc-option, -mstack-alignment=16),)
+	cc_stack_align := -mstack-alignment=16
+endif
+
+CFLAGS_dcn20_resource.o := -mhard-float -msse $(cc_stack_align)
 
 AMD_DAL_DCN20 = $(addprefix $(AMDDALPATH)/dc/dcn20/,$(DCN20))
 

drivers/gpu/drm/amd/display/dc/dsc/Makefile

 #
 # Makefile for the 'dsc' sub-component of DAL.
 
-CFLAGS_rc_calc.o := -mhard-float -msse -mpreferred-stack-boundary=4
-CFLAGS_rc_calc_dpi.o := -mhard-float -msse -mpreferred-stack-boundary=4
-CFLAGS_codec_main_amd.o := -mhard-float -msse -mpreferred-stack-boundary=4
-CFLAGS_dc_dsc.o := -mhard-float -msse -mpreferred-stack-boundary=4
+ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
+	cc_stack_align := -mpreferred-stack-boundary=4
+else ifneq ($(call cc-option, -mstack-alignment=16),)
+	cc_stack_align := -mstack-alignment=16
+endif
+
+dsc_ccflags := -mhard-float -msse $(cc_stack_align)
+
+CFLAGS_rc_calc.o := $(dsc_ccflags)
+CFLAGS_rc_calc_dpi.o := $(dsc_ccflags)
+CFLAGS_codec_main_amd.o := $(dsc_ccflags)
+CFLAGS_dc_dsc.o := $(dsc_ccflags)
 
 DSC = dc_dsc.o rc_calc.o rc_calc_dpi.o