support `-gline-tables-only`

[dschuff]

-gline-tables-only is a useful if somewhat obscure flag in clang which causes the compiler to generate line table debug info but not full info (e.g. source variables). It's useful for allowing e.g. symbolized stack traces without having all of the debug info (which is nice in large programs). It also happens to fit quite well with the current status quo of web debugging which is source-maps-only, and the fact that binaries bloated with huge debug info are more annoying in wasm (even for local debugging) than native (since loading the binary is more costly than loading a native binary). So it would be nice to at least pass the option through to clang; it probably also makes sense to preserve the name section in this case.