Remove '-v' flag from vcheck mode determination

[sibcse]

In most compilers, the -v flag merely enables verbose output, which is different from --version or similar. However, the compiler wrapper switches into 'vcheck' mode if this flag is present, and does not apply any extra search paths or libraries as it should. Thus, if any package (e.g., in a Makefile) introduces a -v flag to the compilation or linking commands, it fails.

This PR simply removes the -v from the list of flags that are used to determine the 'vcheck' mode.

[haampie]

Thanks! I think this is reasonable, but I vaguely recall that there was a reason to special-case -v, namely to prevent an exit code 1 that happened because Spack's compiler flags were added. Let's see what CI thinks of it in practice.

[haampie]

This is what I had in mind: llvm/llvm-project#116799

clang -v -Wl,-rpath,foo

This invokes the linker and errors. Spack adds -Wl,-rpath,...