Fixed nested project issues in msbuild

[svick]

Fixes #7040

[dnfclas]

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[dnfclas]

@svick, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, DNFBOT;

[stephentoub]

LGTM

[ellismg]

LGTM as well. Thanks for the contribution, @svick!