procattr.c: Use __BIONIC__ instead of __ANDROID__

This check is not specific to Android devices. If libselinux were used
with Bionic on a normal Linux system this check would still be needed.

Signed-off-by: Tom Cherry <tomcherry@google.com>

libselinux/src/procattr.c

@@ -22,8 +22,8 @@ static pthread_key_t destructor_key;
 static int destructor_key_initialized = 0;
 static __thread char destructor_initialized;
 
-#ifndef __ANDROID__
-/* Android declares this in unistd.h and has a definition for it */
+#ifndef __BIONIC__
+/* Bionic declares this in unistd.h and has a definition for it */
 static pid_t gettid(void)
 {
 	return syscall(__NR_gettid);