[PATCH v3 1/1] tools/tests/x86_emulator: avoid duplicate symbol error with clang: use -O0

[Edwin Török <edwin.torok@xxxxxxxxxx>]

clang would duplicate the loop body and end up with a double definition
of the symbol:
```
/tmp/test_x86_emulator-0f3576.s:27823: Error: symbol `vmovsh_to_mem' is already 
defined
/tmp/test_x86_emulator-0f3576.s:27825: Error: symbol `.Lvmovsh_to_mem_end' is 
already defined
```

Until a better solution is found: disable all optimizations in the test runner.

Using -Os might also work, but we can't rely on the size optimization
always avoiding the duplication of asm blocks.
This is test code, not performance critical code, and -O0 is more future
proof.

Signed-off-by: Edwin Török <edwin.torok@xxxxxxxxxx>
---
Changed since v2:
 * use -O0 instead of .ifndef (with ifndef the 2nd iteration would use code 
identical to first)
Changed since v1:
 * use .ifndef directive instead of volatile workaround
---
 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 5003c464f3..ba1d27177f 100644
--- a/tools/tests/x86_emulator/Makefile
+++ b/tools/tests/x86_emulator/Makefile
@@ -323,4 +323,9 @@ x86-emulate.o x86_emulate/%.o: HOSTCFLAGS += -D__XEN_TOOLS__
 $(call cc-option-add,HOSTCFLAGS-toplevel,HOSTCC,-fno-toplevel-reorder)
 test_x86_emulator.o: HOSTCFLAGS += $(HOSTCFLAGS-toplevel)
 
+# clang duplicates inline assembly when unrolling loops,
+# which causes a duplicate label error.
+# Until a better solution is found: disable all optimizations in the test 
runner.
+test_x86_emulator.o: HOSTCFLAGS += -O0
+
 test_x86_emulator.o: $(addsuffix .h,$(TESTCASES)) $(addsuffix 
-opmask.h,$(OPMASK))
-- 
2.47.3