Add --stack-growth to the morestack test compile flags

Author: brson

src/test/run-fail/morestack1.rs

@@ -1,4 +1,5 @@
 // xfail-test
+// compile-flags:--stack-growth
 fn getbig(i: int) {
     if i != 0 {
         getbig(i - 1);

src/test/run-pass/morestack1.rs

@@ -1,4 +1,5 @@
 // xfail-test
+// compile-flags:--stack-growth
 fn getbig(i: int) {
     if i != 0 {
         getbig(i - 1);

src/test/run-pass/morestack2.rs

@@ -1,4 +1,5 @@
 // xfail-test
+// compile-flags:--stack-growth
 fn getbig(i: int) -> int {
     let m = if i >= 0 {
         let j = getbig(i - 1);