[PATCH i-g-t] lib/igt_core: Workaround igt_thread failure when libunwind is not present

[Jeevaka Prabu Badrappan]

igt_thread test expects the test failure accompanied by a stack trace
and it matches the trace prefix "Stack trace: " to determine test result.

With the commit "Add a dummy workaround when libunwind is not present",
this trace prefix "Stack trace: " is not printed, resulting in an
igt_thread test failure.

There are 2 solutions to fix this issue:
1. Print the trace "Stack trace: not implemented"
2. Run the failure test only if libunwind is present.

This patch implements the first approach.

Signed-off-by: Jeevaka Prabu Badrappan <jeevaka.badrappan at intel.com>
---
 lib/igt_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/igt_core.c b/lib/igt_core.c
index f698494e1..b06cdfd89 100644
--- a/lib/igt_core.c
+++ b/lib/igt_core.c
@@ -378,7 +378,7 @@ static int _igt_dynamic_tests_executed = -1;
 static void print_backtrace(void)
 {
 #ifndef HAVE_LIBUNWIND
-	igt_info("backtrace not implemented\n");
+	igt_info("Stack trace: not implemented\n");
 #else
 	unw_cursor_t cursor;
 	unw_context_t uc;
@@ -2242,7 +2242,7 @@ xprintf(const char *fmt, ...)
 static void print_backtrace_sig_safe(void)
 {
 #ifndef HAVE_LIBUNWIND
-	igt_info("backtrace not implemented\n");
+	igt_info("Stack trace: not implemented\n");
 #else
 	unw_cursor_t cursor;
 	unw_context_t uc;
-- 
2.49.0