Fix LIN_ADVANCE + SWITCHING_EXTRUDER stepper directions (#10656)

Marlin/src/module/stepper.cpp

@@ -1646,6 +1646,12 @@ void Stepper::isr() {
       #define SET_E_STEP_DIR(INDEX) do{ if (e_steps) E0_DIR_WRITE(e_steps < 0 ? !INVERT_E## INDEX ##_DIR ^ TEST(INDEX, 0) : INVERT_E## INDEX ##_DIR ^ TEST(INDEX, 0)); }while(0)
     #elif ENABLED(DUAL_X_CARRIAGE) || ENABLED(DUAL_NOZZLE_DUPLICATION_MODE)
       #define SET_E_STEP_DIR(INDEX) do{ if (e_steps) { if (e_steps < 0) REV_E_DIR(); else NORM_E_DIR(); } }while(0)
+    #elif ENABLED(SWITCHING_EXTRUDER)
+      #define SET_E_STEP_DIR(INDEX) do{ if (e_steps) { switch (INDEX) { \
+          case 0: case 1: E0_DIR_WRITE(!INVERT_E0_DIR ^ TEST(INDEX, 0) ^ (e_steps < 0)); break; \
+          case 2: case 3: E1_DIR_WRITE(!INVERT_E1_DIR ^ TEST(INDEX, 0) ^ (e_steps < 0)); break; \
+                  case 4: E2_DIR_WRITE(!INVERT_E2_DIR ^ TEST(INDEX, 0) ^ (e_steps < 0)); \
+      } } }while(0)
     #else
       #define SET_E_STEP_DIR(INDEX) do{ if (e_steps) E## INDEX ##_DIR_WRITE(e_steps < 0 ? INVERT_E## INDEX ##_DIR : !INVERT_E## INDEX ##_DIR); }while(0)
     #endif