temporarality disabled ARTI-FX in _S builds

There seem to be some incompatibilities when compiling with -O2 (optimize for speed). Root cause still unclear - further investigation needed.

platformio.ini

@@ -908,8 +908,8 @@ build_flags_S =
   ; -D WLED_USE_CIE_BRIGHTNESS_TABLE ;; experimental: use different color / brightness lookup table
   -D USERMOD_AUDIOREACTIVE
   -D UM_AUDIOREACTIVE_USE_NEW_FFT ; use latest (upstream) FFTLib, instead of older library modified by blazoncek. Slightly faster, more accurate, needs 2KB RAM extra   
-  -D USERMOD_ARTIFX ; WLEDMM usermod
-  ; -D WLEDMM_FASTPATH ; WLEDMM experimental option. Reduces audio lag (latency), and allows for faster LED framerates. May break compatibility with previous versions.
+  ; -D USERMOD_ARTIFX  ;; WLEDMM usermod - temporarily moved into "_M", due to problems in "_S" when compiling with -O2
+  ; -D WLEDMM_FASTPATH ;; WLEDMM experimental option. Reduces audio lag (latency), and allows for faster LED framerates. May break compatibility with previous versions.
   ; -D WLED_DEBUG_HEAP ;; WLEDMM enable heap debugging
   ; -D WLED_DISABLE_LOXONE
   ; -D WLED_DISABLE_ALEXA
@@ -925,6 +925,7 @@ animartrix_build_flags = -D USERMOD_ANIMARTRIX ;; WLEDMM usermod: CC BY-NC 3.0 l
 animartrix_lib_deps = https://github.com/netmindz/animartrix.git#f070fefc42febe2de3a2ab5d6d39e78bbc539702
 
 build_flags_M = 
+  -D USERMOD_ARTIFX ; WLEDMM usermod - temporarily moved into "_M", due to problems in "_S" when compiling with -O2
   -D WLED_MAX_USERMODS=25 ; default only 4-6, also for _XL configs takes 25 pointers in memory
   ;; -D ARDUINO_USB_CDC_ON_BOOT=0 ; needed for arduino-esp32 >=2.0.4 ewowi to softhack: move to build_flags_S? - We need a different solution
   -D WLED_USE_MY_CONFIG ; include custom my_config.h ewowi to softhack: redundant as also in build_flags_S?