Allow passing multiple targets to target_compile_options, target_compile_definitions etc.

In modern CMake, we set target-level properties rather than setting CMake-file-scope/directory-scope properties; and this is the case particularly for compile definitions; for example, we use target_compile_options() instead of COMPILE_OPTIONS. However - target_compile_options() and similar functions only apply to a single target a time, while we often want to apply the same options, definitions etc. to multiple targets.

This can be overcome by creating a list of targets and looping over them, invoking target_compile_options() (and other commands) for each of them; but - other commands, like target_link_libraries() for example, are willing to accept multiple targets, or list of targets, from the get-go. It is more convenient for that to be possible.

So, I ask that the commands:

• target_include_directories()
• target_compile_options()
• target_compile_definitions()
• target_compile_features()
• target_link_directories()
• target_link_options()
• target_sources()
• target_precompile_headers()

and any other similar command, be modified to support specifying multiple targets.

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