build: Generalize spi drivers detection

Don't be limited to elan only

libfprint/meson.build

@@ -1,7 +1,7 @@
 spi_sources = []
 spi_headers = []
 
-if 'elanspi' in drivers
+if enabled_spi_drivers.length() > 0
   spi_headers = ['fpi-spi-transfer.h']
   spi_sources = ['fpi-spi-transfer.c']
 endif

meson.build

@@ -97,6 +97,9 @@ cairo_dep = dependency('cairo', required: false)
 # introspection scanning and Gio-2.0.gir
 gobject_introspection = dependency('gobject-introspection-1.0', required: get_option('introspection'))
 
+# SPI
+have_spi = host_machine.system() == 'linux'
+
 # Drivers
 drivers = get_option('drivers').split(',')
 virtual_drivers = [
@@ -137,9 +140,12 @@ default_drivers = [
     'focaltech_moc',
 ]
 
-# SPI
+spi_drivers = [
-if host_machine.system() == 'linux'
+    'elanspi'
-    default_drivers += ['elanspi']
+]
+
+if have_spi
+    default_drivers += spi_drivers
 endif
 
 # FIXME: All the drivers should be fixed by adjusting the byte order.
@@ -178,6 +184,17 @@ if drivers == [ 'default' ]
     drivers = default_drivers
 endif
 
+enabled_spi_drivers = []
+foreach driver : spi_drivers
+    if driver in drivers
+        enabled_spi_drivers += driver
+    endif
+endforeach
+
+if enabled_spi_drivers.length() > 0 and not have_spi
+    error('SPI drivers @0@ are not supported'.format(enabled_spi_drivers))
+endif
+
 driver_helper_mapping = {
     'aes1610' : [ 'aeslib' ],
     'aes1660' : [ 'aeslib', 'aesx660' ],