Fix tests on ARM Linux (#3)

Author: petrochenkov

src/libstd/sys/unix/backtrace/tracing/gcc_s.rs

@@ -53,7 +53,9 @@ pub fn unwind_backtrace(frames: &mut [Frame])
     // See libunwind:src/unwind/Backtrace.c for the return values.
     // No, there is no doc.
     match result_unwind {
-        uw::_URC_END_OF_STACK | uw::_URC_FATAL_PHASE1_ERROR => {
+        // These return codes seem to be benign and need to be ignored for backtraces
+        // to show up properly on all tested platforms.
+        uw::_URC_END_OF_STACK | uw::_URC_FATAL_PHASE1_ERROR | uw::_URC_FAILURE => {
             Ok((cx.idx, BacktraceContext))
         }
         _ => {

src/libstd/sys_common/backtrace.rs

@@ -134,6 +134,7 @@ fn filter_frames(frames: &[Frame],
         "__libc_start_main",
         "__rust_try",
         "_start",
+        "main",
         "BaseThreadInitThunk",
         "__scrt_common_main_seh",
         "_ZN4drop",