icu: small fixes to support Conan 2.0

[jcar87]

Specify library name and version: icu/all

Summary of changes

• Use str(self.ref) to support cross-building in Conan 2
• Compose build and host triplets directly when cross-building for iOS/watchOS/tvOS, while fixing an issue cross-building from an Apple Silicon mac (the build/host triplets would be the same and the scripts were not correctly detecting cross compilation).
• Remove logic for cross-building on Windows as the issue mentioned in the comments is now resolved in 1.57. This, however, still requires a small nudge to the build scripts, which is specific to the icu build system (telling the build scripts that the mh-msys-msvc config fragment is needed).

Other changes

• Clean-up logic to check that the version of Visual Studio/msvc is the minimum required to pass the -FS flag - this is now possible with check_min_vs when passing raise_invalid=False.
• Remove older versions not referenced elsewhere in Conan Center

Manual testing, both working correctly:

• Conan 2.0: native build on macOS and cross-build to iOS with arm64 and armv7s
• Conan 1.x: Windows, native build and cross-build to ARM64

[ghost]

I detected other pull requests that are modifying icu/all recipe:

• icu: validate dat package file exists #14980

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[SpaceIm]

Are they valid triplet? I mean if arch is armv8, triplet should be aarch64-apple not armv8-apple.

[SpaceIm]

I've tested and icu doesn't seem to complain.

[jcar87]

Indeed - in a config.sub this is likely to be appear like:

| arm | arm[lb]e | arme[lb] | armv* \

so it will work as long as the build scripts don't have further conditionals on the specific arch part of the triple. ICU doesn't seem too bothered. Even when building natively on apple silicon, the arch is autodetected as arm (and not aarch64 like a more modern config.sub would do).

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 1 (f4e2ec7bd692d68284caee707008365e8d1e8054):

• icu/71.1@:
  All packages built successfully! (All logs)

• icu/69.1@:
  All packages built successfully! (All logs)

• icu/72.1@:
  All packages built successfully! (All logs)

• icu/70.1@:
  All packages built successfully! (All logs)

• icu/68.2@:
  All packages built successfully! (All logs)

---

Conan v2 pipeline (informative, not required for merge) ✔️

Note: Conan v2 builds are informative and they are not required for the PR to be merged.

All green in build 1 (f4e2ec7bd692d68284caee707008365e8d1e8054):

• icu/68.2@:
  All packages built successfully! (All logs)

• icu/70.1@:
  All packages built successfully! (All logs)

• icu/72.1@:
  All packages built successfully! (All logs)

• icu/69.1@:
  All packages built successfully! (All logs)

• icu/71.1@:
  All packages built successfully! (All logs)