Don't build SPI driver on non-Linux

Doesn't build on other operating systems.
With auto-detection we don't have to manually select all other drivers.

Signed-off-by: Daniel Schaefer <dhs@frame.work>

libfprint/meson.build

@@ -1,9 +1,9 @@
+spi_sources = []
+spi_headers = []
+
 if 'elanspi' in drivers
   spi_headers = ['fpi-spi-transfer.h']
   spi_sources = ['fpi-spi-transfer.c']
-else
-  spi_sources = []
-  spi_headers = []
 endif
 
 libfprint_sources = [

meson.build

@@ -135,10 +135,12 @@ default_drivers = [
     'fpcmoc',
     'realtek',
     'focaltech_moc',
+]
 
 # SPI
-    'elanspi',
-]
+if host_machine.system() == 'linux'
+    default_drivers += ['elanspi']
+endif
 
 # FIXME: All the drivers should be fixed by adjusting the byte order.
 # See https://gitlab.freedesktop.org/libfprint/libfprint/-/issues/236