libroot: Flesh out glibc floating point support for ARM.

The last time someone touched this directory, there was no floating
point support configured in ARM. Now we are targeting ARMv7a+, which
alwa

libroot: Flesh out glibc floating point support for ARM.

The last time someone touched this directory, there was no floating
point support configured in ARM. Now we are targeting ARMv7a+, which
always has a hard FPU, so we need this now.

With this, a haiku.hpkg can (finally) be built again (at least
under lld, anyway!)

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