wpa-supplicant: Package shared library into wpa-supplicant-lib

When CONFIG_BUILD_WPA_CLIENT_SO is enabled, package the library into
wpa-supplicant-lib.

Signed-off-by: Alex Kiernan <alexk@zuma.ai>
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>