android: Install the libmpd.so output on android

[DDRBoxman]

libmpd.so was getting written as a file called arm64-v8a instead of arm64-v8a/libmpd.so

[MaxKellermann]

This time you're adding a Python script instead of a shell script, which is better... but this still looks more complicated than it should be. Isn't there another, simpler way to do this?
Also your old commit 906d58a looks pretty wrong. It does not properly declare the target file; it pretends to output to OUTPUT/android/apk/libmpd.so (via output: parameter) but it really copies to meson.current_source_dir()/.... - due to this mistake, Ninja is unable to find the output file and thus copies the file again even if it already exists.

[DDRBoxman]

Looks like output is just for names and can't take a path. Setting up the install path and calling install might be an option?

[DDRBoxman]

Okay, switched this over to use install