extends: http://stackoverflow.com/questions/19272127/sdk-location-not-found-android-studio-gradle
I had very similar situation (had a project on another machine and cloned it to my laptop and saw the same issue) and I looked in it.
Error message was coming from Sdk.groovy of Android gradle plugin: https://android.googlesource.com/platform/tools/build/+/master/gradle/src/main/groovy/com/android/build/gradle/internal/Sdk.groovy
By looking at code, its findLocation needs to set androidSdkDir variable and there are only three ways to do it:
create local.properties file and have either sdk.dir or android.dir line.
have ANDROID_HOME environment variable defined.
System.getProperty("android.home") - I'm not sure how it works, but it seems like a Java thing.
While your Android Studio knows that the SDK is at that place, I doubt that Android Studio is passing that information to gradle and thus we're seeing that error.
I created local.properties file at the project root and put the following line and it compiled the code successfully.
sdk.dir = /Applications/Android Studio.app/sdk/