• Remove vestigial arm/arm TARGET/TARGET_ARCH links. The only SoC image that was built was the GUMSTIX image, which had been removed from the tree.
• Add powerpc/powerpcspe, arm/armv7 GENERICSD, and arm64/aarch64 PINE64-LTS for 12.0-CURRENT.
• Fix links in the (not visible) betarel.current links to change arm/armv6 to arm/armv7 where appropriate.
• Comment the signatures.html page for 12.0 until it is ready to be used.
• Change a missed 'IGNORE' to 'INCLUDE' from a previous commit.

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