pass additional flags to ensure static linking GNUTOOLS-15343

When trying to run the mingw toolchain, the compiler couldnt not find the required dll files specifically
libwinpthread-1.dll, it appears we were already trying to statically link this with -Bstatic,-lpthread
but it seems these additional flags are required.
macos clang compiler cannot statically link

Change-Id: I28778592fbeeb5350e5450cfc65ae65606e3fac7