wasm: force static builds

This removes the need for specifying "-static" on the
configure line.

Shared builds are on the roadmap (QTBUG-63925), but
not currently supported.

Change-Id: I7f72ac702bc77304abfa6a962cb1139c25fb5e35
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

configure.json

@@ -582,7 +582,7 @@
         "shared": {
             "label": "Building shared libraries",
             "autoDetect": "!config.uikit",
-            "condition": "!config.integrity",
+            "condition": "!config.integrity && !config.wasm",
             "output": [
                 "shared",
                 "publicFeature",