hardware::Atreus: Only compile the plugin when building for Atreus

With moving to a monorepo, the plugin will always be compiled, so we want to
guard ourselves, to only compile when building for the Atreus. We do this with
an `#ifdef ARDUINO_AVR_ATREUS` guard.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

src/kaleidoscope/hardware/Atreus.cpp

@@ -24,6 +24,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#ifdef ARDUINO_AVR_ATREUS
+
 #include <Kaleidoscope.h>
 #include <KeyboardioHID.h>
 #include <avr/wdt.h>
@@ -291,3 +293,5 @@ void Atreus::debounceRow(uint16_t change, uint8_t row) {
 
 HARDWARE_IMPLEMENTATION KeyboardHardware;
 kaleidoscope::hardware::Atreus &Atreus = KeyboardHardware;
+
+#endif

src/kaleidoscope/hardware/Atreus.h

@@ -24,6 +24,8 @@
 
 #pragma once
 
+#ifdef ARDUINO_AVR_ATREUS
+
 #include <Arduino.h>
 
 #define HARDWARE_IMPLEMENTATION kaleidoscope::hardware::Atreus
@@ -234,3 +236,5 @@ constexpr byte R3C10 = keyIndex(3, 10);
 constexpr byte R3C11 = keyIndex(3, 11);
 
 extern kaleidoscope::hardware::Atreus &Atreus;
+
+#endif