cmake: arm64: Bail out if the old SDK is used

After the ARM/ARM64 split the SDK 0.12.4 is needed to be able to compile
the ARM64 arch code. Bail out if an old SDK is detected at compile time.

Also change the minimal supported Zephyr SDK to v0.12, as agreed in
Toolchain WG.  Main reason is added compiler architectures and important
inclusion of fixes, for example qemu and arm fixes for veneers (TFM)

Signed-off-by: Carlo Caione <ccaione@baylibre.com>