arduinofft: Move to submodule, define srqt_internal externally

Author: FintasticMan

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "src/libs/QCBOR"]
 	path = src/libs/QCBOR
 	url = https://github.com/laurencelundblade/QCBOR.git
+[submodule "src/libs/arduinoFFT"]
+	path = src/libs/arduinoFFT
+	url = https://github.com/kosme/arduinoFFT.git

src/CMakeLists.txt

@@ -672,9 +672,9 @@ set(INCLUDE_FILES
         heartratetask/HeartRateTask.h
         components/heartrate/Ppg.h
         components/heartrate/HeartRateController.h
-        libs/arduinoFFT-develop/src/arduinoFFT.h
-        libs/arduinoFFT-develop/src/defs.h
-        libs/arduinoFFT-develop/src/types.h
+        libs/arduinoFFT/src/arduinoFFT.h
+        libs/arduinoFFT/src/defs.h
+        libs/arduinoFFT/src/types.h
         components/motor/MotorController.h
         buttonhandler/ButtonHandler.h
         touchhandler/TouchHandler.h

src/components/heartrate/Ppg.h

@@ -5,8 +5,9 @@
 #include <cstdint>
 // Note: Change internal define 'sqrt_internal sqrt' to
 // 'sqrt_internal sqrtf' to save ~3KB of flash.
+#define sqrt_internal sqrtf
 #define FFT_SPEED_OVER_PRECISION
-#include "libs/arduinoFFT-develop/src/arduinoFFT.h"
+#include "libs/arduinoFFT/src/arduinoFFT.h"
 
 namespace Pinetime {
   namespace Controllers {