Global: workaround toolchain problem on windows

The minimum version for gcc was supposed to be 4.9 for any platform.
However our build instructions are outdated. Remove the problematic
parts that use the sparse-endian.h header while we don't fix the setup
for windows.

libraries/AP_ADC/AP_ADC_ADS1115.cpp

@@ -1,4 +1,7 @@
 #include <AP_HAL/AP_HAL.h>
+
+#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+
 #include <AP_HAL/utility/sparse-endian.h>
 
 #include "AP_ADC_ADS1115.h"
@@ -236,3 +239,5 @@ void AP_ADC_ADS1115::_update()
 
     _last_update_timestamp = AP_HAL::micros();
 }
+
+#endif

libraries/AP_Compass/AP_Compass_HMC5843.cpp

@@ -24,6 +24,8 @@
  */
 #include <AP_HAL/AP_HAL.h>
 
+#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+
 #ifdef HAL_COMPASS_HMC5843_I2C_ADDR
 
 #include <assert.h>
@@ -591,3 +593,5 @@ bool AP_HMC5843_BusDriver_Auxiliary::start_measurements()
 }
 
 #endif
+
+#endif