This reverts commit 82377a787a.

Reintegrates changes from cf9fc84669

Similar code was incorrectly removed in
070a6b35e9.

When using CLion to invoke CMake, using a Clang toolchain and Ninja, and
targeting x64, CLion will pass -m64 in CMAKE_C_FLAGS and
CMAKE_CXX_FLAGS. The compilers are passed through to the juceaide build,
but the target arch was not, which meant that the linker attempted to
link x86 libraries, which failed.

This fixes an issue where the app icon would not be visible for
standalone plugin targets.

In order to display a WebKit based webview a plugin will deploy a
temporary standalone executable on the system and host the WebKit
instance inside that.

JUCE no longer depends on built artifacts of the AAX_SDK

When building for arm64 with a VS generator on a x86_64 host,
CMAKE_CROSSCOMPILING is not set, and copying the generator platform can
result in a juceaide binary that doesn't run on the host system.

The removed code no longer seems to be necessary when configuring with
newer Clion versions.

The ARA_SDK contains unguarded is_lock_free calls. This change
allows us to enable ARA compilation on Linux.

This issue made hosts not recognize the ARA capabilities of AU plugins.