Fix #14880 add support for Folders in slnx project file and skip non C++ projects #20173

Job	Run time
build_cmake (alpine:3.23, false, false)	3m 51s
build_cmake (ubuntu:25.10, true, true)	2m 39s
build_cmake (ubuntu:24.04, true, true)	5m 2s
build_make (ubuntu:24.04)	4m 14s
build_make (alpine:3.23)	5m 59s
build_make (ubuntu:25.10)	5m 8s
	26m 53s

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