Avoid defining _LIBCPP_ELAST (#17021)

sbc100 · web-flow · commit e6f29a6cd284 · 2022-05-23T13:09:51.000-07:00
Several other targets including WASI already do this.  It
looks like it saves a little on codesize and is only used
to improve reporting in some cases.  If its not defined the
error strings get a little more generic.

For example in __generic_error_category::message:

```
string
__generic_error_category::message(int ev) const
{
#ifdef _LIBCPP_ELAST   
    if (ev &gt; _LIBCPP_ELAST)
      return string("unspecified generic_category error");
#endif // _LIBCPP_ELAST 
    return __do_message::message(ev);
}
```
diff --git a/system/lib/libcxx/src/include/config_elast.h b/system/lib/libcxx/src/include/config_elast.h
@@ -33,8 +33,8 @@
 #define _LIBCPP_ELAST 4095
 #elif defined(__APPLE__)
 // No _LIBCPP_ELAST needed on Apple
-#elif defined(__EMSCRIPTEN__) // XXX EMSCRIPTEN added ELAST value
-#define _LIBCPP_ELAST 256
+#elif defined(__EMSCRIPTEN__)
+// No _LIBCPP_ELAST needed on Emscripten
 #elif defined(__sun__)
 #define _LIBCPP_ELAST ESTALE
 #elif defined(__MVS__)
diff --git a/tests/other/metadce/test_metadce_cxx_except.size b/tests/other/metadce/test_metadce_cxx_except.size
@@ -1 +1 @@
-165393
+165383
diff --git a/tests/other/metadce/test_metadce_cxx_except_wasm.size b/tests/other/metadce/test_metadce_cxx_except_wasm.size
@@ -1 +1 @@
-135983
+135973
diff --git a/tests/other/metadce/test_metadce_cxx_mangle.size b/tests/other/metadce/test_metadce_cxx_mangle.size
@@ -1 +1 @@
-225971
+225961
