build: check minimum ICU in configure for system-icu

[srl295]

• check the version number coming out of pkg-config

Fixes: #24253

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

@srl295 build started: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/1545/pipeline

[srl295]

else you get this:

root@4f4928358b09:/src/node# ./configure --with-intl=system-icu ERROR: icu4c v60.2 is too old, v99.x or later is required. 

also updates config.gypi, which wasn't set before. (icu_system_version is new here. icu_ver_major was set by the 'icu generic.gyp' code path, but not by system-icu previously)

'icu_system_version': '60.2','icu_ver_major': '60',

[bnoordhuis]

If nothing uses/is going to use icu_system_version, can you remove it?

[srl295]

@bnoordhuis I'll remove icu_system_version but keep icu_ver_major for consistency with the other path.

[srl295]

@bnoordhuis thanks. I think I addressed your comments.

[bnoordhuis]

LGTM with a comment.

[Trott]

@srl295 Looks like there's one nit from @bnoordhuis and a CI run and otherwise this is landable? Does that seem right to you?

[refack]

CI: https://ci.nodejs.org/job/node-test-pull-request/18690/

[refack]

CI: https://ci.nodejs.org/job/node-test-pull-request/18691/