Add test for delay_span_bug and -Ztrear-err-as-bug

Author: spastorino

src/test/run-make-fulldeps/treat-err-as-bug/Makefile

@@ -3,3 +3,5 @@
 all:
 	$(RUSTC) err.rs -Z treat-err-as-bug 2>&1 \
 	    | $(CGREP) "panicked at 'aborting due to \`-Z treat-err-as-bug=1\`'"
+	$(RUSTC) delay_span_bug.rs -Z treat-err-as-bug 2>&1 \
+	    | $(CGREP) "panicked at 'aborting due to \`-Z treat-err-as-bug=1\`'"

src/test/run-make-fulldeps/treat-err-as-bug/delay_span_bug.rs

@@ -0,0 +1,4 @@
+#![feature(rustc_attrs)]
+
+#[rustc_error(delay_span_bug_from_inside_query)]
+fn main() {}