Add test to check behavior when incremental session init fails.

Author: ehuss

src/test/run-make/incremental-session-fail/Makefile

@@ -0,0 +1,15 @@
+include ../../run-make-fulldeps/tools.mk
+
+SESSION_DIR := $(TMPDIR)/session
+OUTPUT_FILE := $(TMPDIR)/build-output
+
+all:
+	echo $(TMPDIR)
+	mkdir $(SESSION_DIR)
+	# Make it so that rustc will fail to create a session directory.
+	chmod a-w $(SESSION_DIR)
+	# Check exit code is 1 for an error, and not 101 for ICE.
+	$(RUSTC) foo.rs --crate-type=rlib -C incremental=$(SESSION_DIR) > $(OUTPUT_FILE) 2>&1; [ $$? -eq 1 ]
+	$(CGREP) "Could not create incremental compilation crate directory" < $(OUTPUT_FILE)
+	# -v tests are fragile, hopefully this text won't change
+	$(CGREP) -v "internal compiler error" < $(OUTPUT_FILE)

src/test/run-make/incremental-session-fail/foo.rs

@@ -0,0 +1 @@
+// intentionally empty