x86: cover for clang's lack of support of -mpreferred-stack-boundary=<N>

While clang supposedly supports -mstack-alignment=<N> instead, I'm not
using that alternative here due to being uncertain whether that's indeed
an exact equivalent of the gcc option. Only make use of the option
entirely conditional for now.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/efi/Makefile b/xen/arch/x86/efi/Makefile
index f223ef058ef7120eb02876b3e4f474f016cf187c..4bc0a196e9ca4dce26376a05ca68b300388d94d3 100644 (file)
--- a/xen/arch/x86/efi/Makefile
+++ b/xen/arch/x86/efi/Makefile
@@ -7,7 +7,8 @@ boot.init.o: buildid.o
 
 EFIOBJ := boot.init.o compat.o runtime.o
 
-$(EFIOBJ): CFLAGS-stack-boundary := -mpreferred-stack-boundary=4
+$(call cc-option-add,cflags-stack-boundary,CC,-mpreferred-stack-boundary=4)
+$(EFIOBJ): CFLAGS-stack-boundary := $(cflags-stack-boundary)
 
 obj-y := stub.o
 obj-$(XEN_BUILD_EFI) := $(EFIOBJ) relocs-dummy.o