build, tools, win: enable build without nasm

[shigeki]

Do not terminate vcbuild.bat even if nasm is not found on Windows.
In that case, configure emits a warning message and continues to build
Node.js with openssl_no_asm option enabled.

This cannot be checked with CI for nasm was already installed.
The following the output of vcbuild.bat on my Windows after uninstalling nasm.

CC @joaocgreis and @nodejs/build

Looking for Python 2.x
Looking for NASM
Looking for Visual Studio 2017
Found MSVS version 15.0
configure  --dest-cpu=x64
WARNING: No acceptable ASM compiler found!
         Please make sure you have installed nasm from http://www.nasm.us
         and refer BUILDING.md.
WARNING: openssl_no_asm is enabled due to missed or old assembler.
            Please refer BUILDING.md
creating icu_config.gypi
* Using ICU in deps/icu-small
creating icu_config.gypi
{ 'target_defaults': { 'cflags': [],
                       'default_configuration': 'Release',
                       'defines': [],
                       'include_dirs': [],
                       'libraries': []},
  'variables': { 'asan': 0,
                 'coverage': 'false',
                 'debug_http2': 'false',
                 'debug_nghttp2': 'false',
                 'force_dynamic_crt': 0,
                 'host_arch': 'x64',
                 'icu_data_in': '..\\..\\deps/icu-small\\source/data/in\\icudt61l.dat',
                 'icu_endianness': 'l',
                 'icu_gyp_path': 'tools/icu/icu-generic.gyp',
                 'icu_locales': 'en,root',
                 'icu_path': 'deps/icu-small',
                 'icu_small': 'true',
                 'icu_ver_major': '61',
                 'nasm_version': 0,
                 'node_byteorder': 'little',
                 'node_debug_lib': 'false',
                 'node_enable_d8': 'false',
                 'node_enable_v8_vtunejit': 'false',
                 'node_install_npm': 'true',
                 'node_module_version': 62,
                 'node_no_browser_globals': 'false',
                 'node_prefix': '/usr/local',
                 'node_release_urlbase': '',
                 'node_shared': 'false',
                 'node_shared_cares': 'false',
                 'node_shared_http_parser': 'false',
                 'node_shared_libuv': 'false',
                 'node_shared_nghttp2': 'false',
                 'node_shared_openssl': 'false',
                 'node_shared_zlib': 'false',
                 'node_tag': '',
                 'node_target_type': 'executable',
                 'node_use_bundled_v8': 'true',
                 'node_use_dtrace': 'false',
                 'node_use_etw': 'true',
                 'node_use_openssl': 'true',
                 'node_use_perfctr': 'true',
                 'node_use_v8_platform': 'true',
                 'node_without_node_options': 'false',
                 'openssl_fips': '',
                 'openssl_no_asm': 1,
                 'shlib_suffix': 'so.62',
                 'target_arch': 'x64',
                 'v8_enable_gdbjit': 0,

Fixes: #19918

Checklist

• [x ] make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• [x ] commit message follows commit guidelines

[bzoz]

CI: https://ci.nodejs.org/job/node-test-pull-request/14197/

[bzoz]

Since this unbreaks master, I think we should fast-track this.

[rvagg]

I'm +1 on @bnoordhuis' suggestion of making it fail unless you explicitly opt out #19918 (comment)

[rvagg]

@bzoz master isn't broken, it's just giving a message that inconsistent with its behaviour. It's inconvenient and confusing for users but for those building from source we should be giving a stronger recommendation to grab nasm.

[shigeki]

Closing by #19943.