Fix _mongoc_get_cpu_count on Android (#1084)

* fix: _mongoc_get_cpu_count on android: get_nprocs is not available on Android below API level 23.
* Always use sysconf for Linux

Co-authored-by: ii14 <[email protected]>
Co-authored-by: vector-of-bool <[email protected]>

Author: ii14

src/libmongoc/src/mongoc/mongoc-counters-private.h

@@ -48,8 +48,12 @@ _mongoc_counters_cleanup (void);
 static BSON_INLINE unsigned
 _mongoc_get_cpu_count (void)
 {
-#if defined(__linux__)
-   return get_nprocs ();
+#if defined(__linux__) && defined(_SC_NPROCESSORS_CONF)
+   long count = sysconf (_SC_NPROCESSORS_CONF);
+   if (count < 1) {
+      return 1;
+   }
+   return count;
 #elif defined(__hpux__)
    struct pst_dynamic psd;