Disable fdtrack post-fork.

Also delete some fdsan code that attempts to check for the post-fork
state, but never will, because we update the cached pid upon fork.

Bug: http://b/174542867
Test: /data/nativetest64/bionic-unit-tests/bionic-unit-tests
Test: treehugger
Change-Id: I9b748dac9de9b4c741897d93e64d31737e52bf8e
diff --git a/libc/bionic/fdtrack.cpp b/libc/bionic/fdtrack.cpp
index 1123512..89a208f 100644
--- a/libc/bionic/fdtrack.cpp
+++ b/libc/bionic/fdtrack.cpp
@@ -37,8 +37,14 @@
 
 _Atomic(android_fdtrack_hook_t) __android_fdtrack_hook;
 
+bool __android_fdtrack_globally_disabled = false;
+
+void android_fdtrack_set_globally_enabled(bool new_value) {
+  __android_fdtrack_globally_disabled = !new_value;
+}
+
 bool android_fdtrack_get_enabled() {
-  return !__get_bionic_tls().fdtrack_disabled;
+  return !__get_bionic_tls().fdtrack_disabled && !__android_fdtrack_globally_disabled;
 }
 
 bool android_fdtrack_set_enabled(bool new_value) {