Fix ui/io-checks/inaccessbile-temp-dir.rs test

Author: WaffleLapkin

tests/run-make/inaccessbile-temp-dir/Makefile

@@ -0,0 +1,31 @@
+# only-linux
+
+include ../tools.mk
+
+# Issue #66530: We would ICE if someone compiled with `-o /dev/null`,
+# because we would try to generate auxiliary files in `/dev/` (which
+# at least the OS X file system rejects).
+#
+# An attempt to `-Ztemps-dir` into a directory we cannot write into should
+# indeed be an error; but not an ICE.
+#
+# However, some folks run tests as root, which can write `/dev/` and end
+# up clobbering `/dev/null`. Instead we'll use an inaccessible path, which
+# also used to ICE, but even root can't magically write there.
+#
+# Note that `-Ztemps-dir` uses `create_dir_all` so it is not sufficient to
+# use a directory with non-existing parent like `/does-not-exist/output`.
+
+all:
+	# Create an inaccessible directory
+	mkdir $(TMPDIR)/inaccessible
+	chmod 000 $(TMPDIR)/inaccessible
+
+	# Run rustc with `-Ztemps-dir` set to a directory 
+	# *inside* the inaccessible one, so that it can't create it
+	$(RUSTC) program.rs -Ztemps-dir=$(TMPDIR)/inaccessible/tmp 2>&1 \
+		| $(CGREP) "failed to find or create the directory specified by `--temps-dir`"
+
+	# Make the inaccessible directory accessible,
+	# so that compiletest can delete the temp dir
+	chmod +rw $(TMPDIR)/inaccessible

tests/run-make/inaccessbile-temp-dir/program.rs

@@ -0,0 +1 @@
+fn main() {}