Revert "bootstat: Remove custom uptime parser in favor of elapsedRealtime."

This reverts commit 26f40c04c3ad80e2bc449990010d39d1c1b9a5f0.

This change broke the Darwin SDK target.

Test: none
Change-Id: Ia54fe2c31da8d8fa2825e023b035fb8321dcd457
diff --git a/bootstat/Android.bp b/bootstat/Android.bp
index 7d9d7a2..d98a9d7 100644
--- a/bootstat/Android.bp
+++ b/bootstat/Android.bp
@@ -17,6 +17,7 @@
 bootstat_lib_src_files = [
     "boot_event_record_store.cpp",
     "histogram_logger.cpp",
+    "uptime_parser.cpp",
 ]
 
 cc_defaults {