fix buldled static build on Windows/MinGW (#761)

seems like need more libraries in LDFLAGS:

* ws2_32 for socket, connect, htonl, etc
* ole32 for CoInitializeEx
* rpcrt4 for UuidCreate
* crypt32 for CertFreeCertificateContext

Author: vladimir-buzuev

Build_bundled_static.go

@@ -4,7 +4,7 @@ package git
 
 /*
 #cgo windows CFLAGS: -I${SRCDIR}/static-build/install/include/
-#cgo windows LDFLAGS: -L${SRCDIR}/static-build/install/lib/ -lgit2 -lwinhttp
+#cgo windows LDFLAGS: -L${SRCDIR}/static-build/install/lib/ -lgit2 -lwinhttp -lws2_32 -lole32 -lrpcrt4 -lcrypt32
 #cgo !windows pkg-config: --static ${SRCDIR}/static-build/install/lib/pkgconfig/libgit2.pc
 #cgo CFLAGS: -DLIBGIT2_STATIC
 #include <git2.h>