swift234

Convert "armv7l" to "armv7" for the architecture component of paths (#2369)

On the Raspberry Pi 2 when trying to import Glibc, without this patch, it will attempt to
find the module map at "/usr/lib/swift/linux/armv7l/glibc.modulemap" and
fail to do so.

With this patch it will attempt to find the module map at
"/usr/lib/swift/linux/armv7/glibc.modulemap" where it will succeed in
finding the module map.

Similar behavior currently happens in the Driver and Frontend. To DRY up
this behavior it has been extracted to the Swift platform.