Move the addLayerIfAvailable() anonymous function to the condition where
it's actually used. Otherwise we get
"error: unused variable 'addLayerIfAvailable' [-Werror,-Wunused-variable]"

Bug: b/185779640
Change-Id: I2aaa0656bfcb0c1c0aa14c44837cf1b46ea02f54
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/53988
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>