This reverts commit 82377a787a.

JUCE no longer depends on built artifacts of the AAX_SDK

Xcode 14 has minimum deployment targets of macos 10.13 and iOS 11.

Mirrors the behaviour of CMake by only adding signing identity field to
project when identity is not empty.

This reverts commit 8bacf8c15c.

This reverts commit a71bda9adb.

By default, x86_64 binaries are not signed, but arm64 binaries are. When
building universal binaries, it was possible to end up with a final
artefact that contains an unsigned x86_64 image, but a signed arm64
image. In some cases, this could cause issues in subsequent codesign
invocations.