[msbuild] Improve how we handle the path to Xcode.

[rolfbjarne]

• Add support for an MSBuild property ('XcodeLocation') to set the Xcode location.
• Use a new facility in macios-devtools (the 'XcodeLocator' class) to find Xcode. This required a bump to the corresponding submodule.
• Deprecate the file-based locations.
• Always set DEVELOPER_DIR when executing subprocesses.
• Don't use static state to store the Xcode location. This fixes a problem where the static state would remain in memory when MSBuild's build server is being used, and then we'd do the wrong thing when building a different project using a different version of Xcode.

Misc improvements:

• We now warn if the selected Xcode is a symlink (ref: ACTool task fails to build when the currently selected Xcode is a symlink #21762).
• The settings files are deprecated, and won't be used in .NET 11 (we'll warn about this in .NET 10).
• The environment variable MD_APPLE_SDK_ROOT is deprecated, and won't be used in .NET 11 (we'll warn about this in .NET 10).

This will hopefully remove some confusion about which Xcode is being used; now we just look at the system's Xcode, unless it's overridden by the MSBuild property 'XcodeLocation'.

Fixes #3931.
Fixes #11172.
Fixes #21762.

[vs-mobiletools-engineering-service2]

💻 [CI Build #f9b9cfc] Tests on macOS M1 - Mac Monterey (12) passed 💻

✅ All tests on macOS M1 - Mac Monterey (12) passed.

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Hash: f9b9cfcc3127b7cdcab80284bfac19f6accfcc6c [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #f9b9cfc] Tests on macOS X64 - Mac Sonoma (14) passed 💻

✅ All tests on macOS X64 - Mac Sonoma (14) passed.

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Hash: f9b9cfcc3127b7cdcab80284bfac19f6accfcc6c [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #f9b9cfc] Tests on macOS M1 - Mac Ventura (13) passed 💻

✅ All tests on macOS M1 - Mac Ventura (13) passed.

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Hash: f9b9cfcc3127b7cdcab80284bfac19f6accfcc6c [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #f9b9cfc] Tests on macOS arm64 - Mac Sequoia (15) passed 💻

✅ All tests on macOS arm64 - Mac Sequoia (15) passed.

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Hash: f9b9cfcc3127b7cdcab80284bfac19f6accfcc6c [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #f9b9cfc] Tests on macOS arm64 - Mac Tahoe (26) passed 💻

✅ All tests on macOS arm64 - Mac Tahoe (26) passed.

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Hash: f9b9cfcc3127b7cdcab80284bfac19f6accfcc6c [PR build]

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✅ [CI Build #c221335] Build passed (Build packages) ✅

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Hash: c22133546877a3d3973430f844d13516999a0b32 [PR build]

[vs-mobiletools-engineering-service2]

✅ [PR Build #c221335] Build passed (Detect API changes) ✅

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Hash: c22133546877a3d3973430f844d13516999a0b32 [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

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Hash: c22133546877a3d3973430f844d13516999a0b32 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #c221335] Build passed (Build macOS tests) ✅

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Hash: c22133546877a3d3973430f844d13516999a0b32 [PR build]

[vs-mobiletools-engineering-service2]

🔥 [CI Build #c221335] Test results 🔥

Test results

❌ Tests failed on VSTS: test results

1 tests crashed, 0 tests failed, 151 tests passed.

Failures

❌ Tests on macOS Sonoma (14) tests

🔥 Failed catastrophically on VSTS: test results - mac_sonoma (no summary found).

Html Report (VSDrops) Download

Successes

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 6 tests passed. Html Report (VSDrops) Download
✅ linker: All 44 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 11 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 15 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 12 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 11 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

✅ Tests on macOS Monterey (12): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Ventura (13): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sequoia (15): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Tahoe (26): All 5 tests passed. Html Report (VSDrops) Download

Linux Build Verification

✅ Linux build succeeded

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Hash: c22133546877a3d3973430f844d13516999a0b32 [PR build]