Add a wasm code size test for stringifying numbers

src/test/run-make/wasm-stringify-ints-small/Makefile

@@ -0,0 +1,10 @@
+-include ../../run-make-fulldeps/tools.mk
+
+ifeq ($(TARGET),wasm32-unknown-unknown)
+all:
+	$(RUSTC) foo.rs -C lto -O --target wasm32-unknown-unknown
+	wc -c < $(TMPDIR)/foo.wasm
+	[ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "21000" ]
+else
+all:
+endif

src/test/run-make/wasm-stringify-ints-small/foo.rs

@@ -0,0 +1,39 @@
+#![crate_type = "cdylib"]
+
+extern "C" {
+    fn observe(ptr: *const u8, len: usize);
+
+    fn get_u8() -> u8;
+    fn get_i8() -> i8;
+    fn get_u16() -> u16;
+    fn get_i16() -> i16;
+    fn get_u32() -> u32;
+    fn get_i32() -> i32;
+    fn get_u64() -> u64;
+    fn get_i64() -> i64;
+    fn get_usize() -> usize;
+    fn get_isize() -> isize;
+}
+
+macro_rules! stringify {
+    ( $($f:ident)* ) => {
+        $(
+            let s = $f().to_string();
+            observe(s.as_ptr(), s.len());
+        )*
+    };
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn foo() {
+    stringify!(get_u8);
+    stringify!(get_i8);
+    stringify!(get_u16);
+    stringify!(get_i16);
+    stringify!(get_u32);
+    stringify!(get_i32);
+    stringify!(get_u64);
+    stringify!(get_i64);
+    stringify!(get_usize);
+    stringify!(get_isize);
+}