Move static variable out of should_trace().

Static variable initialization calls pthread_mutex_lock() and may lead to
deadlock if should_trace() is called in pthread_mutex_lock context.

Here is a stack of blocked init process:
__cxa_guard_acquire ->
should_trace        ->
bionic_trace_begin  ->
__pthread_mutex_lock_with_timeout ->
__cxa_guard_release ->
should_trace        ->
bionic_trace_begin  ->
__pthread_mutex_lock_with_timeout ->
mutex::lock        ->
LogMessage::~LogMessage
......
So we need to move it out

Test: 1 Compiled and booted.
      2 Reboot pressure test for more than 30000 times.

Change-Id: I8d97745161f1aa8942b63338208ea74830768ae1
Signed-off-by: Wei Li <sirius.liwei@huawei.com>
Signed-off-by: Jinguang Dong <dongjinguang@huawei.com>
diff --git a/libc/bionic/bionic_systrace.cpp b/libc/bionic/bionic_systrace.cpp
index 970a92b..bac3d88 100644
--- a/libc/bionic/bionic_systrace.cpp
+++ b/libc/bionic/bionic_systrace.cpp
@@ -29,12 +29,11 @@
 #define WRITE_OFFSET   32
 
 static Lock g_lock;
+static CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags");
+static uint64_t g_tags;
 static int g_trace_marker_fd = -1;
 
 static bool should_trace() {
-  static CachedProperty g_debug_atrace_tags_enableflags("debug.atrace.tags.enableflags");
-  static uint64_t g_tags;
-
   g_lock.lock();
   if (g_debug_atrace_tags_enableflags.DidChange()) {
     g_tags = strtoull(g_debug_atrace_tags_enableflags.Get(), nullptr, 0);