[lld] [lld][llvm-lit] Enabled lit internal shell for lld test suite (PR #106651)

[Connie Zhu via llvm-commits]

connieyzhu wrote:

> How many tests have `REQUIRES: shell` in the lld testsuite?

There are 7 tests:
./lld/test/wasm/lto/cache-warnings.ll
./lld/test/wasm/reproduce.s
./lld/test/ELF/linkerscript/invalid.test
./lld/test/ELF/lto/resolution-err.ll
./lld/test/ELF/color-diagnostics.test
./lld/test/MachO/color-diagnostics.test
./lld/test/COFF/color-diagnostics.test


> I have real concerns that we'll end up with tests that are NEVER enabled, because nobody is going to explicitly specify to use the external shell.

We do have long-term plans to address this issue with `REQUIRES: shell`, but I'm not sure what can be done in the short-term so that we don't lose coverage.

https://github.com/llvm/llvm-project/pull/106651