Incorrect assumption about file name patterns in table build

[jphickey]

Describe the bug
On most CMake platforms the generated object file names are simply the file name (including the .c) concatenated with CMAKE_C_OUTPUT_EXTENSION. So, for example, on table build for sample_app, the file sample_app_tbl.c gets compiled into sample_app_tbl.c.o which can then be used to call elf2cfetbl.

Apparently this relationship is not guaranteed, there is at least one example of a platform where this gets compiled to sample_app_tbl.o instead of sample_app_tbl.c.o.

To Reproduce
Attempt to build on a platform that does not follow the expected pattern. Tables will fail to build with a failure to open the object file due to the name mismatch.

Expected behavior
Table should build successfully.

Code snips
I traced this back to a workaround that was put in for older CMake, which assumes the name of the object file:

cFE/cmake/arch_build.cmake

Lines 200 to 201 in 73c338d

	get_filename_component(TBLOBJ ${TBL} NAME)
	string(APPEND TBLOBJ ${CMAKE_C_OUTPUT_EXTENSION})

The preferred/correct way to do this is to use the $<TARGET_OBJECTS:...> generator expression, but this only works in newer CMake versions. The workaround was to assume a file name based on the expected pattern, which works most of the time, but there are exceptions.

System observed on:
Originally reported by @klystron78 when building for VxWorks 7.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.