kernel-build-tools: Add BoringSSL headers and libcrypto

Add the development headers for BoringSSL to the kernel build tools
distribution. In addition, add a symbolic link
libcrypto.so -> libcrypto-host.so into the distribution.

That way we can use this as a drop in replacement for OpenSSL during
kernel builds (effectively getting rid of the host openssl dependency).

Bug: 135570712
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: Ie013ce0e354e196229e41e37900e79ba14dcf0f0