qt5base-lts/mkspecs/features/wasm/emcc_ver.prf

defineReplace(qtEmccRecommendedVersion) {
    return (1.39.8)
}

defineReplace(qtSystemEmccVersion) {
    EMCC = $$system("emcc -v 2>&1", lines)
    EMCC_LINE = $$find(EMCC, "^.*\b(emcc)\b.*$")
    E_VERSION = $$section(EMCC_LINE, " ", 9,9)
    return ($${E_VERSION})
}

defineTest(qtConfTest_emccVersion) {

    REQ_VERSION = $$qtEmccRecommendedVersion()
    EMCC_VERSION = $$qtSystemEmccVersion()

    !defined(QT_EMCC_VERSION, var):!equals(EMCC_VERSION, $${REQ_VERSION}) {
        warning ("You should use the recommended Emscripten version $$REQ_VERSION with this Qt. You have $${EMCC_VERSION} ")
    }
    contains(TEMPLATE, .*app) {
           !equals(QT_EMCC_VERSION, $$EMCC_VERSION)  {
               warning("This Qt was built with Emscripten version $${QT_EMCC_VERSION}. You have $${EMCC_VERSION}. The difference may cause issues.")
           }
    }
}