I've created a self-compiled Qt for Android from Git stable and
added it as a kit to QtCreator. If this kit is selected the
"run" and "start debugging" buttons are grayed out.

If I switch to a kit with a Qt version build from Qt5.2-beta1 tag, the
buttons get enabled again.

Additionally, if I right-click on my project and select "deploy" I get
the following message:

No Android arch set by the .pro file.
Error while building/deploying project myproject (kit: Android-X86)
When executing step 'Deploy to Android device'

I've tried defining ANDROID_TARGET_ARCH and ANDROID_ARCH in my .pro
file as a work-around, but that didn't help.

It looks like this issue was introduced in qtbase between Qt 5.2-beta1 and now.