Android Gradle failed to build: Caused by: groovy.lang.MissingMethodException: No signature of method

Can't build my Ionic Capacitor app in Android Studio, something has broken the entire app. After running npx cap open android, Android Studio opens and I get the error message

org.gradle.api.GradleScriptException: A problem occurred evaluating project ':app'.
    ...
Caused by: groovy.lang.MissingMethodException: No signature of method: build_aox2ttoqa9ez79ar8j35lengn.android() is applicable for argument types: (build_aox2ttoqa9ez79ar8j35lengn$_run_closure1) values: [build_aox2ttoqa9ez79ar8j35lengn$_run_closure1@2161bb28]

My build.gradle (app) file:

apply plugin: 'com.android.application'

android {
    // useLibrary  'org.apache.http.legacy'
    compileSdkVersion rootProject.ext.compileSdkVersion
    defaultConfig {
        applicationId "io.ionic.easyscoreapp"
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode 7.1
        versionName "7.1.1"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        aaptOptions {
             // Files and dirs to omit from the packaged assets dir, modified to accommodate modern web apps.
             // Default: https://android.googlesource.com/platform/frameworks/base/+/282e181b58cf72b6ca770dc7ca5f91f135444502/tools/aapt/AaptAssets.cpp#61
            ignoreAssetsPattern '!.svn:!.git:!.ds_store:!*.scc:.*:!CVS:!thumbs.db:!picasa.ini:!*~'
        }
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

repositories {
    flatDir{
        dirs '../capacitor-cordova-android-plugins/src/main/libs', 'libs'
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "androidx.appcompat:appcompat:$androidxAppCompatVersion"
    implementation project(':capacitor-android')
    testImplementation "junit:junit:$junitVersion"
    androidTestImplementation "androidx.test.ext:junit:$androidxJunitVersion"
    androidTestImplementation "androidx.test.espresso:espresso-core:$androidxEspressoCoreVersion"
    implementation project(':capacitor-cordova-android-plugins')
}

apply from: 'capacitor.build.gradle'

try {
    def servicesJSON = file('google-services.json')
    if (servicesJSON.text) {
        apply plugin: 'com.google.gms.google-services'
    }
} catch(Exception e) {
    logger.info("google-services.json not found, google-services plugin not applied. Push Notifications won't work")
}

And my build.gradle file is:

ext {
    cordovaAndroidVersion = project.hasProperty('cordovaAndroidVersion') ? rootProject.ext.cordovaAndroidVersion : '7.0.0'
}

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.2.1'
    }
}

apply plugin: 'com.android.library'

android {
    compileSdkVersion project.hasProperty('compileSdkVersion') ? rootProject.ext.compileSdkVersion : 30
    defaultConfig {
        minSdkVersion project.hasProperty('minSdkVersion') ? rootProject.ext.minSdkVersion : 21
        targetSdkVersion project.hasProperty('targetSdkVersion') ? rootProject.ext.targetSdkVersion : 30
        versionCode 1
        versionName "1.0"
    }
    lintOptions {
        abortOnError false
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

repositories {
    google()
    jcenter()
    mavenCentral()
    flatDir{
        dirs 'src/main/libs', 'libs'
    }
}

dependencies {
    implementation fileTree(dir: 'src/main/libs', include: ['*.jar'])
    implementation "org.apache.cordova:framework:$cordovaAndroidVersion"
    // SUB-PROJECT DEPENDENCIES START

    // SUB-PROJECT DEPENDENCIES END
}

// PLUGIN GRADLE EXTENSIONS START
apply from: "cordova.variables.gradle"
// PLUGIN GRADLE EXTENSIONS END

for (def func : cdvPluginPostBuildExtras) {
    func()
}

These files are mostly build automatically by Ionic and Capacitor, so no changes made by me in there.