etc: Add helgrind suppressions for libunwind

Author: brson

src/etc/x86.supp

@@ -435,4 +435,29 @@
    fun:_ZN15lock_and_signal4lockEv
    fun:_ZN18rust_port_selector6selectEP9rust_taskPP9rust_portS4_mPm
    ...
-}
+}
+
+{
+   libunwind-surely-this-is-ok
+   Helgrind:Race
+   ...
+   fun:_Unwind_RaiseException
+   fun:__cxa_throw
+   ...
+}
+
+{
+   libunwind-surely-this-is-ok2
+   Helgrind:Race
+   ...
+   fun:_Unwind_Resume
+   ...
+}
+
+{
+   libunwind-surely-this-is-ok3
+   Helgrind:Race
+   fun:_Unwind_SetGR
+   fun:__gxx_personality_v0
+   ...
+}