fix conditional-uninitialized warnings

Summary: D92969284 promotes conditional-uninitialized to a compiler error fbobjc-wide. Initialize variables to safe defaults in wa-msys (_WCIZlib.c, _WAMTransportPrivateUtil.c), msys/mci (MCIGraphQLValidationUtils.c), mci/trace (MCITrace.c), and thrift (TBufferTransports.cpp).

Reviewed By: ethansinjin

Differential Revision: D93137196

fbshipit-source-id: 4b9ef480eb59234858fb98d9ad965a0fbcb4f9f3

Author: David Wolstencroft

thrift/lib/cpp/transport/TBufferTransports.cpp

@@ -212,7 +212,7 @@ bool TFramedTransport::readFrame(uint32_t /*minFrameSize*/) {
   // We can't use readAll(&sz, sizeof(sz)), since that always throws an
   // exception on EOF.  We want to throw an exception only if EOF occurs after
   // partial size data.
-  uint32_t sz;
+  uint32_t sz = 0;
   uint32_t size_bytes_read = 0;
   while (size_bytes_read < sizeof(sz)) {
     uint8_t* szp = reinterpret_cast<uint8_t*>(&sz) + size_bytes_read;