New Gradle project (command-line and single-module) can't find Android plugin - android-gradle-plugin

Question

I had a single-module project working in command-line Ant and want to convert it to Gradle but it fails at: 'gradle tasks', because it can't find the Android plugin.
This failure coincided with an upgrade to the Android SDK/Tools & Support Repository.
I'm using windows 10 and the TextPad editor (DOS command line screen is included).
The Gradle version is 2.12
build.gradle:
apply plugin: 'com.android.library'
android{
compileSdkVersion 20
buildToolsVersion '23'
System.properties['com.android.build.gradle.overrideVersionCheck'] = 'true'
repositories{
jcenter()
}
dependencies{
classpath 'com.android.tools.build:gradle:1.1.0'
}
}
Note:
I've tried moving the repositories and dependencies out from under the android {}'s.
Error Message:
FAILURE: Build failed with an exception.
* Where:
Build file 'D:\Android\Clox\build.gradle' line: 1
* What went wrong:
A problem occurred evaluating root project 'Clox'.
Plugin with id 'com.android.library' not found.
local.properties file:
sdk.dir=c:\users\chatt\AppData\Local\Android\sdk1
or
sdk.dir=C\:\\Users\\chatt\\AppData\\Local\\Android\\sdk1
I included this because it seems to ignore my JDK_HOME.
JDK_HOME started off pointing at JAVA_HOME. I tried changing JDK_HOME to: 'XXX' and it just gave the usual error.
JDK_HOME is now c:\users\chatt\AppData\Local\Android\sdk1, which I got from the header of the Android SDK Manager, and ANDROID_HOME=%JDK_HOME%.
RECENT TESTING:
I had a sequence of errors that I found the answers to in:
https://stackoverflow.com/questions/
(thank you people)
and then I updated the JDK, adding the Build Tools, with the results:
Packages
- Android SDK Tools, revision 25.1.1
- Android SDK Build-tools, revision 23.0.3
...
- Android Support Repository, revision 30
plus I see there is installed:
-Android SDK Platform 6.0 (API 23)
-Android Support Library v.23.2.1
Apparently this update is what caused the com.android.library plugin not found error; apart from a JAVA_HOME error that's all it gives me.

Answer 1

Apparently my build.gradle structure was wasn't sufficiently standard.
I've switched to a version from:
http://tools.android.com/tech-docs/new-build-system/user-guide
buildscript {
System.properties['com.android.build.gradle.overrideVersionCheck'] = 'true'
repositories {
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:1.5.0'
}
}
apply plugin: 'com.android.library'
android {
compileSdkVersion 23
buildToolsVersion "23.0.3"
}