Support cross-compiling in the libmagic vcpkg port overlay. (#5333) #1182

Job	Run time
Package-Source-Release (ubuntu-20.04)	4m 42s
Package-Binary-Release (macos-arm64)	20m 53s
Package-Binary-Release (macos-x86_64)	22m 30s
Package-Binary-Release (linux-x86_64)	2m 36s
Package-Binary-Release (linux-x86_64-noavx2)	2m 30s
Package-Binary-Release (windows-x86_64)	28m 40s
Test-Release-Artifacts	0s
Publish-Release	0s
Create-Issue-On-Fail	6s
Generate-Release-List	0s
	1h 21m 57s

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