ci: Build MacVim test binaries separately from running tests #1038

Job	Run time
build-and-test (macos-14, 15.4, false) / build-and-test	9m 42s
build-and-test (macos-13, 15.2, true, vimtags, check-xcodeproj-compat) / build-and-test	18m 8s
build-and-test (macos-15, 16.4, true, true, true) / build-and-test	24m 18s
build-and-test (macos-13-xcode14-self-hosted, true, _10.9, true, true) / build-and-test	0s
	52m 8s

Provide feedback