attempt to fix openssl pkg-config find fail?

update llvm-mingw

fix zlib for Windows (stunnel#145)

* fix zlib for Windows

try unpinning nghttp for 8.16.0

build libs with -Os -ffunction-sections -fdata-sections

to allow for smaller binaries if the --gc-sections linker flag is used

build static libs for linux (glibc) and windows x86_64/i686