Audio demos/tests: Only limit latency adjustment to Linux + ARM.

IsARM() is insufficient to decide if latency requirements should be loosened.
The assumption was that IsARM == RaspberryPi, but now IsARM can also mean
rather powerful Apple Silicon ARM SoC's like M1/M2/M3/M4/... and those do not
need loose latency requirements. So only loosen if ARM + Linux. This is still a bit
ham fisted as there are many other ARM SoC's under Linux than RaspberryPi
which are swept up in this wide net. Baby steps.

Psychtoolbox/PsychDemos/BasicAMAndMixScheduleDemo.m

@@ -42,7 +42,7 @@ function BasicAMAndMixScheduleDemo(device)
 nrchannels = 2;
 sugLat = [];
 
-if IsARM
+if IsARM && IsLinux
     % ARM processor, probably the RaspberryPi SoC. The Pi can not quite handle the
     % low latency settings of a desktop PC, so be more lenient:
     sugLat = 0.025;

Psychtoolbox/PsychDemos/BasicSoundScheduleDemo.m

@@ -86,7 +86,7 @@ function BasicSoundScheduleDemo(wavfilenames, device)
 InitializePsychSound;
 
 suggestedLatencySecs = [];
-if IsARM
+if IsARM && IsLinux
     % ARM processor, probably the RaspberryPi SoC. This can not quite handle the
     % low latency settings of a Intel PC, so be more lenient:
     suggestedLatencySecs = 0.025;

Psychtoolbox/PsychTests/PsychPortAudioDataPixxTimingTest.m

@@ -126,7 +126,7 @@ function PsychPortAudioDataPixxTimingTest(waitTime, exactstart, deviceid, latbia
 buffersize = 0;     % Pointless to set this. Auto-selected to be optimal.
 suggestedLatencySecs = [];
 
-if IsARM
+if IsARM && IsLinux
     % ARM processor, probably the RaspberryPi SoC. This can not quite handle the
     % low latency settings of a Intel PC, so be more lenient:
     suggestedLatencySecs = 0.025;

Psychtoolbox/PsychTests/PsychPortAudioTimingTest.m

@@ -128,7 +128,7 @@ function PsychPortAudioTimingTest(exactstart, deviceid, latbias, waitframes, use
 buffersize = 0;     % Pointless to set this. Auto-selected to be optimal.
 suggestedLatencySecs = [];
 
-if IsARM
+if IsARM && IsLinux
     % ARM processor, probably the RaspberryPi SoC. This can not quite handle the
     % low latency settings of a Intel PC, so be more lenient:
     suggestedLatencySecs = 0.025;