Introduce CLR_CMAKE_TARGET_APPLE_MOBILE for iOS/tvOS/MacCatalyst

[steveisok]

These three platforms share the same runtime constraints: static linking, no fork(), no build tools, hybrid globalization, no console signals, etc. Having each one listed individually in cmake conditions is verbose and error-prone — PR #126550 accidentally disabled FEATURE_CORPROFILER for tvOS alone, breaking unified-build tvOS legs.

Introduce CLR_CMAKE_TARGET_APPLE_MOBILE as an umbrella variable in configureplatform.cmake, set when any of iOS, tvOS, or MacCatalyst is the target. Replace ~30 'all three grouped' patterns across 11 cmake files with the umbrella, reducing line noise and preventing future divergence.

Per-platform variables are preserved where they genuinely differ:

• configurecompiler.cmake: TARGET_* C++ defines and compiler targets
• System.Security.Cryptography.Native.Apple: Swift platform names
• System.Net.Security.Native / corehost: tvOS gssapi exclusion
• System.Native: MacCatalyst pal_iossupportversion.m

Also fixes: sendfile exclusion was missing MacCatalyst (now covered by APPLE_MOBILE), and the triplicated configure.cmake feature overrides for iOS/MacCatalyst/tvOS are consolidated into one block.

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[Copilot]

Pull request overview

Introduces a new CMake umbrella variable, CLR_CMAKE_TARGET_APPLE_MOBILE, to represent iOS/tvOS/MacCatalyst collectively, reducing duplicated platform conditionals and helping avoid unintended per-platform divergence in build feature logic.

Changes:

• Define CLR_CMAKE_TARGET_APPLE_MOBILE in eng/native/configureplatform.cmake when targeting iOS, tvOS, or MacCatalyst.
• Replace repeated (MACCATALYST OR IOS OR TVOS) / negated variants across CoreCLR and native libraries CMake files with the new umbrella variable.
• Consolidate several Apple-mobile-specific configure-time feature overrides (e.g., sendfile probing and TRY_RUN-derived feature defaults) under the umbrella check.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
eng/native/configureplatform.cmake	Defines CLR_CMAKE_TARGET_APPLE_MOBILE and uses it for zlib/tooling platform gating.
src/native/libs/configure.cmake	Uses the umbrella to gate sendfile probes and Apple-mobile TRY_RUN overrides / header availability flags.
src/native/libs/CMakeLists.txt	Uses umbrella for Apple-mobile install-name handling and to exclude System.IO.Ports.Native on Apple-mobile targets.
src/coreclr/CMakeLists.txt	Uses umbrella to skip single-file host build on Apple-mobile targets.
src/coreclr/clrfeatures.cmake	Uses umbrella to drive FEATURE_STATICALLY_LINKED for Apple-mobile targets.
src/native/libs/System.Native/CMakeLists.txt	Replaces Apple-mobile platform triplets in console-signals and entrypoint-verification gating.
src/native/libs/System.Globalization.Native/CMakeLists.txt	Replaces Apple-mobile platform triplets for hybrid globalization + ICU/static-ICU behavior.
src/native/libs/System.IO.Compression.Native/CMakeLists.txt	Replaces Apple-mobile platform triplets for export generation / entrypoints inclusion gating.
src/native/libs/System.IO.Compression.Native/extra_libs.cmake	Uses umbrella for Apple-mobile zlib link behavior selection.
src/native/libs/System.Net.Security.Native/CMakeLists.txt	Replaces Apple-mobile platform triplets in entrypoints inclusion and verification gating.
src/native/libs/System.Security.Cryptography.Native.Apple/CMakeLists.txt	Uses umbrella to select iOS-family keychain/x509 source set and entrypoint-verification gating.

[jkoritzinsky]

LGTM once @akoeplinger's feedback is resolved.