Non-static kernel code functions within the tested packages cannot be mocked

[ilansmith]

A non-static function implemented in some ut/<feature>/*.c file cannot have a corresponding mock function in kernel/emu/lnx/* for other features and tests to use. This will result in a linkage multiple definition conflict. There needs to be a way to avoid linking in within the same build both a kernel implementation function and its corresponding mock within the kunit framework.

[ilansmith]

The way to do this is probably to use GCC's -z muldefs linkage option. However, we need to make sure that the correct symbol is used in each context. That is, when function foo() is being tested, the testing code must call its under test kernel implementation (in ut//). However, when foo() gets called by other parts of the test framework or even from other packages under test - its mock implementation must be called (in kernel/emu/lnx/).