This extends the target selection implemented in dad6ec3aa63f to support
Windows ARM64 platforms.  OpenSSL support for VC-WIN64-ARM target first
appeared in 1.1.1 and is present in all currently supported (3.x)
branches.

As a side effect, ARM64 Windows builds will get 16-byte alignment along
with the rest of non-x86 platforms.  This is safe, as malloc on 64-bit
Windows guarantees the fundamental alignment of allocations, 16 bytes.

To ensure proper target selection the NGX_MACHINE variable is now set
based on the MSVC compiler output, and the OpenSSL target is set based
on it.

This is not important as long as "no-asm" is used (as in misc/GNUmakefile
and win32 build instructions), but might be beneficial if someone is trying
to build OpenSSL with assembler code.

This was previously used, but was incorrectly removed in 83d54192e97b
while removing old threads remnants.  Instead of using it conditionally
when threads are not used, we now set in unconditionally, as even with
thread pools enabled we never call OpenSSL functions in threads.

This fixes resulting binary when using --with-openssl with OpenSSL 1.1.0+
and without -lpthread linked (notably on FreeBSD without PCRE).

The install_sw target first appeared in OpenSSL 0.9.7e and is documented since
OpenSSL 1.0.0 as the way to install the OpenSSL software without documentation.

This change allows to build nginx against git checkout of OpenSSL.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

make installs the libraries in lib64 directory

*) style fix