Revert "Revert "Added a bionic systrace class and tracing to pthread_mutex.cpp.""

This reverts commit 26c1420fbb68916d66a8621b5efe8bb25cfdad7b.
diff --git a/libc/Android.mk b/libc/Android.mk
index 5052cb1..5f5add2 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -89,6 +89,7 @@
     bionic/access.cpp \
     bionic/assert.cpp \
     bionic/atof.cpp \
+    bionic/bionic_systrace.cpp \
     bionic/bionic_time_conversions.cpp \
     bionic/brk.cpp \
     bionic/c16rtomb.cpp \