__ANDROID__ is the correct macro to check for an android system.ANDROID is only defined in NDK build system (.mk) and not in the standalone NDK.

include/SDL_egl.h

@@ -420,7 +420,7 @@ typedef struct gbm_device  *EGLNativeDisplayType;
 typedef struct gbm_bo      *EGLNativePixmapType;
 typedef void               *EGLNativeWindowType;
 
-#elif defined(ANDROID) /* Android */
+#elif defined(__ANDROID__) /* Android */
 
 struct ANativeWindow;
 struct egl_native_pixmap_t;

include/SDL_rwops.h

@@ -93,7 +93,7 @@ typedef struct SDL_RWops
     Uint32 type;
     union
     {
-#if defined(ANDROID)
+#if defined(__ANDROID__)
         struct
         {
             void *fileNameRef;

src/audio/SDL_audio.c

@@ -305,7 +305,7 @@ SDL_StreamDeinit(SDL_AudioStreamer * stream)
 }
 #endif
 
-#if defined(ANDROID)
+#if defined(__ANDROID__)
 #include <android/log.h>
 #endif
 

src/file/SDL_rwops.c

@@ -38,7 +38,7 @@
 #include "cocoa/SDL_rwopsbundlesupport.h"
 #endif /* __APPLE__ */
 
-#ifdef ANDROID
+#ifdef __ANDROID__
 #include "../core/android/SDL_android.h"
 #include "SDL_system.h"
 #endif
@@ -466,7 +466,7 @@ SDL_RWFromFile(const char *file, const char *mode)
         SDL_SetError("SDL_RWFromFile(): No file or no mode specified");
         return NULL;
     }
-#if defined(ANDROID)
+#if defined(__ANDROID__)
 #ifdef HAVE_STDIO_H
     /* Try to open the file on the filesystem first */
     if (*file == '/') {

test/testautomation_rwops.c

@@ -309,7 +309,7 @@ rwops_testFileRead(void)
    if (rw == NULL) return TEST_ABORTED;
 
    /* Check type */
-#if defined(ANDROID)
+#if defined(__ANDROID__)
    SDLTest_AssertCheck(
       rw->type == SDL_RWOPS_STDFILE || rw->type == SDL_RWOPS_JNIFILE,
       "Verify RWops type is SDL_RWOPS_STDFILE or SDL_RWOPS_JNIFILE; expected: %d|%d, got: %d", SDL_RWOPS_STDFILE, SDL_RWOPS_JNIFILE, rw->type);
@@ -356,7 +356,7 @@ rwops_testFileWrite(void)
    if (rw == NULL) return TEST_ABORTED;
 
    /* Check type */
-#if defined(ANDROID)
+#if defined(__ANDROID__)
    SDLTest_AssertCheck(
       rw->type == SDL_RWOPS_STDFILE || rw->type == SDL_RWOPS_JNIFILE,
       "Verify RWops type is SDL_RWOPS_STDFILE or SDL_RWOPS_JNIFILE; expected: %d|%d, got: %d", SDL_RWOPS_STDFILE, SDL_RWOPS_JNIFILE, rw->type);