Appending '-L' flags to the rustc command is not possible, preventing sysroot-like library resolution

[codyps]

I'm running into this with yocto/openembedded:

• oe supplies a sysroot containing a bunch of native libs and normally adjusts LDFLAGS to point gcc at it.
• We can adjust the linker via .cargo/config to include the specified LDFLAGS, however
• rustc also appears to do it's own library resolution prior to linking, and doesn't know about any of the extra paths passed via the linker argument, and bails out with something like:

error: could not find native static libraryz, perhaps an -L flag is missing?

[alexcrichton]

Note that this is part of the motivation for rust-lang/rfcs#403. For now you can set RUST_PATH to work around this (not exactly a long-term solution though)

[codyps]

Thanks for the pointer at RUST_PATH.

[alexcrichton]

This has now been implemented via #792. Cargo does not support -L flags at the CLI level, but build scripts can now feed back into the rustc commands about where native libraries are located if they're discovered. For that reason, I'm going to close this for now.