rust: don't export cxx syms from libunwind-rust

repos/libports/lib/mk/libunwind-rust.mk

@@ -3,3 +3,19 @@ LIBS = libcore-rust
 vpath % $(REP_DIR)/src/lib/rust/libunwind
 
 CC_CXX_WARN_STRICT =
+
+#
+# libunwind contains the public symbol '_Unwind_Resume', which clashes with
+# the symbol provided by the cxx library. The aliasing can lead to unexpected
+# symbol resolutions by the dynamic linker at runtime, i.e., a C++ exception
+# thrown in the libc ending up in the '_Unwind_Resume' code of libunwind-rust.
+#
+# This rule solves this uncertainty by making the symbol private to the
+# libunwind library.
+#
+ifeq ($(called_from_lib_mk),yes)
+$(LIB).lib.a: hide_cxx_symbols
+hide_cxx_symbols: lib.o
+	$(VERBOSE)cp $< $<.tmp
+	$(VERBOSE)$(OBJCOPY) --localize-symbol=_Unwind_Resume $<.tmp $<
+endif