build: don't guess where a feature may be available

Test the feature, not the OS. Fixes Android build.

configure.in

@@ -863,7 +863,7 @@ AC_FUNC_STRFTIME
 AC_FUNC_STRTOD
 AC_FUNC_UTIME_NULL
 AC_FUNC_VPRINTF
-AC_CHECK_FUNCS([atexit dup2 fdatasync floor fs_stat_dev ftime ftruncate getcwd gethostbyaddr gethostbyname gethostname getpagesize getpass gettimeofday inet_ntoa lchown localeconv memchr memmove memset mkdir modf munmap pow rmdir select setenv setlocale socket sqrt strcasecmp strchr strcspn strdup strerror strncasecmp strpbrk strrchr strspn strstr strtol strtoul sysinfo tzset utime])
+AC_CHECK_FUNCS([atexit dup2 fdatasync floor fs_stat_dev ftime ftruncate getcwd gethostbyaddr gethostbyname gethostname getpagesize getpass gettimeofday inet_ntoa lchown localeconv memchr memmove memset mkdir modf munmap pow rmdir select setenv setlocale socket sqrt strcasecmp strchr strcspn strdup strerror strncasecmp strpbrk strrchr strspn strstr strtol strtoul sysinfo tzset utime posix_fadvise])
 
 # Check for various sizes
 AC_CHECK_SIZEOF([int])

xbmc/filesystem/HDFile.cpp

@@ -211,7 +211,7 @@ unsigned int CHDFile::Read(void *lpBuf, int64_t uiBufSize)
   if ( ReadFile((HANDLE)m_hFile, lpBuf, (DWORD)uiBufSize, &nBytesRead, NULL) )
   {
     m_i64FilePos += nBytesRead;
-#if defined(TARGET_LINUX)
+#if defined(HAVE_POSIX_FADVISE)
     // Drop the cache between where we last seeked and 16 MB behind where
     // we are now, to make sure the file doesn't displace everything else.
     // However, we never throw out the first 16 MB of the file, as we might