extmod/modplatform: Add Android to the recognised platforms list.

This commit adds code to distinguish between regular Linux and Android,
also adding a specific entry for the platform libc.  The reported libc
is marked as "bionic" and its version matches the Android platform API
version (there are no definitions for a specific bionic version).

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

Author: agatti

extmod/modplatform.h

@@ -96,12 +96,17 @@
 #elif defined(_PICOLIBC__)
 #define MICROPY_PLATFORM_LIBC_LIB       "picolibc"
 #define MICROPY_PLATFORM_LIBC_VER       _PICOLIBC_VERSION
+#elif defined(__ANDROID__)
+#define MICROPY_PLATFORM_LIBC_LIB       "bionic"
+#define MICROPY_PLATFORM_LIBC_VER       MP_STRINGIFY(__ANDROID_API__)
 #else
 #define MICROPY_PLATFORM_LIBC_LIB       ""
 #define MICROPY_PLATFORM_LIBC_VER       ""
 #endif
 
-#if defined(__linux)
+#if defined(__ANDROID__)
+#define MICROPY_PLATFORM_SYSTEM         "Android"
+#elif defined(__linux)
 #define MICROPY_PLATFORM_SYSTEM         "Linux"
 #elif defined(__unix__)
 #define MICROPY_PLATFORM_SYSTEM         "Unix"