Fix NSRect init invocation on 32bit platforms

[uraimo]

This fixes an issue in NSGeometry on 32bit platforms selecting the (x: CGFloat, y: CGFloat, width: CGFloat, height: CGFloat) overload, that will just cast a CGFloat::NativeType to, again, a CGFloat::NativeType, platform dependent (either Float or Double).

The error I'm getting right now:

/mnt/buildSwiftOnARM/swift-corelibs-foundation/Foundation/NSGeometry.swift:689:12: error: cannot invoke initializer for type 'NSRect' with an argument list of type '(x: Float, y: Float, width: Float, height: Float)'
    return NSRect(x: x, y: y, width: w, height: h)
           ^
/mnt/buildSwiftOnARM/swift-corelibs-foundation/Foundation/NSGeometry.swift:689:12: note: overloads for 'NSRect' exist with these partially matching parameter lists: (x: CGFloat, y: CGFloat, width: CGFloat, height: CGFloat), (x: Double, y: Double, width: Double, height: Double), (x: Int, y: Int, width: Int, height: Int)
    return NSRect(x: x, y: y, width: w, height: h)
           ^
ninja: build stopped: subcommand failed.
./swift/utils/build-script: fatal error: command terminated with a non-zero exit status 1, aborting

[compnerd]

@swift-ci please test

[compnerd]

@millenomi - okay with you? I believe that this is correct.