[BUG] The legacy toolchain file incorrectly sets `CMAKE_ANDROID_ARM_MODE`

[FooIbar]

Description

CMAKE_ANDROID_ARM_MODE should be ON/OFF per its doc, but the legacy toolchain file will set it to ANDROID_ARM_MODE, which is thumb/arm, so CMAKE_ANDROID_ARM_MODE will always be evaluated as ON.
I'm surprised it's broken since the beginning: https://android-review.googlesource.com/c/platform/ndk/+/360029

I am using a supported NDK

• I have checked and the NDK I'm using is currently supported

Affected versions

r27, r28, r29

[enh-google]

I'm surprised it's broken since the beginning: https://android-review.googlesource.com/c/platform/ndk/+/360029

hmm... that's always one of those weird "maybe this isn't broken so much as unused and best left alone" cases then?

[FooIbar]

It may silently hurt performance/density, but could be hard to notice since it only affects generated instructions rather than causing a build failure.
I only found it when investigating why Corrosion wasn't using the Neon toolchain corrosion-rs/corrosion#661