Add a regression test for #29122 (fixed in #29134)

Author: wthrowe

src/test/run-make/linker-output-non-utf8/Makefile

@@ -0,0 +1,12 @@
+-include ../tools.mk
+
+# Make sure we don't ICE if the linker prints a non-UTF-8 error message.
+
+# The zzz it to allow humans to tab complete or glob this thing.
+bad_dir := $(TMPDIR)/zzz$$'\xff'
+
+all:
+	$(RUSTC) library.rs
+	mkdir $(bad_dir)
+	mv $(call DYLIB,library) $(bad_dir)
+	LIBRARY_PATH=$(bad_dir) $(RUSTC) exec.rs 2>&1 | grep this_symbol_not_defined

src/test/run-make/linker-output-non-utf8/exec.rs

@@ -0,0 +1,6 @@
+#[link(name="library")]
+extern "C" {
+    fn foo();
+}
+
+fn main() { unsafe { foo(); } }

src/test/run-make/linker-output-non-utf8/library.rs

@@ -0,0 +1,9 @@
+#![crate_type = "dylib"]
+
+extern "C" {
+    fn this_symbol_not_defined();
+}
+
+pub extern "C" fn foo() {
+    unsafe { this_symbol_not_defined(); }
+}