upgrade npm to 6.14.6
update openssl to 1.1.1g

Vulnerabilities fixed:
* CVE-2020-8172: TLS session reuse can lead to host certificate verification bypass (High).
* CVE-2020-11080: HTTP/2 Large Settings Frame DoS (Low).
* CVE-2020-8174: napi_get_value_string_*() allows various kinds of memory corruption (High).

Signed-off-by: Hirokazu MORIKAWA <morikw2@gmail.com>

modify host icu library path

Signed-off-by: Hirokazu MORIKAWA <morikw2@gmail.com>

Add some new APIs
V8 was updated to 7.8.279.23. This includes performance improvements to object
destructuring, RegExp match failures and WebAssembly startup time.

Signed-off-by: Hirokazu MORIKAWA <morikw2@gmail.com>

Update to v12.15.0
Support Python3 : https://github.com/openwrt/packages/issues/8893
Preparing to deprecate nosnapshot builds.

Signed-off-by: Hirokazu MORIKAWA <morikw2@gmail.com>