[PATCH v2 2/4] tools/tests/x86_emulator: fix build on clang-21

[Edwin Török <edwin.torok@xxxxxxxxxx>]

clang-21's built-in assembler is enabled by default, but it doesn't
support some mnemonics:
```
test_x86_emulator.c:2636:36: error: invalid instruction mnemonic 'fsaves'
 2636 |                        "fidivs %1\n\t"
test_x86_emulator.c:2640:24: error: invalid instruction mnemonic 'frstors'
 2640 |         asm volatile ( "frstors %0" :: "m" (res[25]) : "memory" );
      |                        ^
test_x86_emulator.c:4251:24: error: invalid instruction mnemonic 'vpcmpestriq'
 4251 |                        put_insn(vpcmpestri,
      |                        ^
```

Use the external assembler with Clang for consistency with GCC.

Signed-off-by: Edwin Török <edwin.torok@xxxxxxxxxx>
---
Changed since v1:
 * filed upstream bug and added reference
---
 tools/tests/x86_emulator/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/tests/x86_emulator/Makefile 
b/tools/tests/x86_emulator/Makefile
index e18725d0c3..5003c464f3 100644
--- a/tools/tests/x86_emulator/Makefile
+++ b/tools/tests/x86_emulator/Makefile
@@ -297,6 +297,11 @@ x86_emulate:
 
 HOSTCFLAGS-x86_64 := -fno-PIE
 $(call cc-option-add,HOSTCFLAGS-x86_64,HOSTCC,-no-pie)
+
+# clang's integrated as does not support some mnemonics:
+#  https://github.com/llvm/llvm-project/issues/183635
+$(call cc-option-add,HOSTCFLAGS-x86_64,HOSTCC,-no-integrated-as)
+
 HOSTCFLAGS += $(CFLAGS_xeninclude) -I. $(HOSTCFLAGS-$(XEN_COMPILE_ARCH))
 
 x86.h := $(addprefix $(XEN_ROOT)/tools/include/xen/asm/,\
-- 
2.47.3