Test COMPILE_DEFINITIONS target property get/set/get round-trip

Teach the Preprocess test to get, set, and then get the same value for
the COMPILE_DEFINITIONS target property and verify that the value is not
changed.  This ensures the internal structured storage of the property
value can reproduce the original string value.
Revert "Differentiate tests."

This reverts commit 444afd91f55fc2e8cabd8d9d275623f9f0f78238.
Revert "Copy the semicolon test from the Preprocess test to CompileDefinitions."

This reverts commit 978b663f1ddcfd8868822038566d206874e62a63.
Merge topic 'compile-defs-debugging' into next

65df537 Revert "Copy the semicolon test from the Preprocess test to CompileDefinitions."
56f5c88 Revert "Differentiate tests."
Merge topic 'compile-defs-debugging' into next

a43e5e0 Test COMPILE_DEFINITIONS target property get/set/get round-trip