libvlc: gdb: fix script

- Fix the ANDROID_MANIFEST path (app/build instead of vlc-android/build).
- Remove useless copies (libs folder, Android.mk, whole obj/local/*/ when only
  the so are needed)
- Configure it only for the arch of the last built APK. This fixes armv7 builds
  that could not be debugged on armv8 arches.
4 jobs for !425 with gdb-fix in 0 seconds (queued for 23 seconds)
detached
Status Job ID Name Coverage
  Build
canceled #350620
android debian
build-libvlc-arm64

canceled #350621
android debian
build-libvlc-armv7

canceled #350622
android debian
build-libvlc-x86

canceled #350623
android debian
build-libvlc-x86_64