Pre-flight SkTLS_pthread changes for C++17

Looks like this is what the CFI bots tripped on,
so maybe there's something more real going on here.

I think we can try again in Chromium after this?

Change-Id: I6f59aeae01df130a21c64b5218b4d21238e343d7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/253636
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/ports/SkTLS_pthread.cpp b/src/ports/SkTLS_pthread.cpp
index c96271b..d017c51 100644
--- a/src/ports/SkTLS_pthread.cpp
+++ b/src/ports/SkTLS_pthread.cpp
@@ -16,7 +16,7 @@
     // should we use forceCreateTheSlot to potentially just return nullptr if
     // we've never been called with forceCreateTheSlot==true ?
     static SkOnce once;
-    once(pthread_key_create, &gSkTLSKey, SkTLS::Destructor);
+    once([]{pthread_key_create(&gSkTLSKey, SkTLS::Destructor);});
     return pthread_getspecific(gSkTLSKey);
 }