haiku - prefer-dynamic bug locating libstd in filesystem

[kallisti5]

Crate: serde -> serde_derive

$ cargo test -p serde_derive --lib
.
.
runtime_loader: Cannot open file libstd-bd738371ca7e9dbf.so (needed by /boot/home/serde/target/debug/deps/serde_derive-48eee61a15dbfe2f): No such file or directory

looking for that shared library:

$ find / -name "libstd-*.so
-r-xr-xr-x 1 user root 1717368 Apr 11 15:18 /boot/system/develop/tools/rust/lib/rustlib/x86_64-unknown-haiku/lib/libstd-bd738371ca7e9dbf.so

The biggest question is what code handles appending the path above to the search path for dynamic libraries? Obviously our system LIBRARY_PATH (1:1 what LD_LIBRARY_PATH is on Linux) won't include /boot/system/develop/tools/rust/lib/rustlib/x86_64-unknown-haiku/lib/.

Here is haiku's LIBRARY_PATH for reference:

LIBRARY_PATH=%A/lib:/boot/home/config/non-packaged/lib:/boot/home/config/lib:/boot/system/non-packaged/lib:/boot/system/lib

[bjorn3]

LD_LIBRARY_PATH is modified on two layers: rustup (to add the compiler libraries for use by rustc) and cargo (to add the standard library and dylib dependencies)

[kallisti5]

Ah! Perfect. cargo doesn't know about Haiku's LIBRARY_PATH. Thank you!

(i'll submit a PR)