Update logic added by commit 099934e313 (Add generator expression
support to static code analysis hooks, 2023-03-24, v3.27.0-rc1~261^2),
and preserved by commit 993dde925f (TargetGenerator: Factor out
generation of code check rules, 2023-05-12, v3.27.0-rc1~84^2~2), to
handle a generator expression that evaluates to the empty string.
If `<LANG>_CPPCHECK`, `<LANG>_CPPLINT`, `<LANG>_CLANG_TIDY`, or
`<LANG>_INCLUDE_WHAT_YOU_USE` are empty after evaluating generator
expressions, do not run their lints.
Fixes: #25265
The `SKIP_LINTING` source property was added to disable code check for
desired source files. The `SKIP_LINTING`includes `cpplint`, `clang-tidy`, \
`cppcheck` and `include-what-you-use`. If `SKIP_LINTING` is set on a
source file, the tools mentioned above will not be run on that source file.
Refactoring in commit v3.10.0-rc1~115^2 (Clean up iwyu code to not be
one big if statement, 2017-08-28) incorrectly changed the logic to run
only one lint tool at a time. Restore support for running all tools
specified on the command-line.
