This was broken by commit df08c37a42 (cmGlobalGenerator: Add unity/pch
sources after computing compile features, 2024-02-02, v3.28.3~1^2~1^2),
and 3.28.2's commit 76b5383123 (cmGlobalGenerator: add unity sources
after computing target compile features, 2024-01-01, v3.28.2~17^2~1).
The problem is very similar to that fixed by commit 4e8f24e977 (PCH:
Clear link interface cache when adding PCH object to it, 2022-01-24,
v3.23.0-rc1~44^2~9). Generalize that fix.
Fixes: #25696
Move the diagnostic that rejects the TARGET_OBJECTS generator expression
in non-buildsystem context until after the check for whether the named
target is an object library. This order will makes more sense than the
previous order once TARGET_OBJECTS is allowed in non-buildsystem
context.
The output of this expression may contain macros for IDEs to replace
such as $(Configuration), $(CURRENT_ARCH) etc. To avoid generating
content which is not usable in other contexts, report an error if
there is an attempt to use it in other contexts.
This commit may be reverted in the future if a solution to the
above difference is implemented.
