`rustc` successfully compiles PIE for target without support for PIE

Code

With the following target spec:

{
  "arch": "x86_64",
  "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128",
  "linker": "rust-lld",
  "linker-flavor": "ld.lld",
  "llvm-target": "x86_64-unknown-none-elf",
  "panic-strategy": "abort",
  "target-pointer-width": "64"
}

(note that position-independent-executables is implicitly set to false)

The following command successfully compiles:

RUSTFLAGS="-Crelocation-model=pie" cargo b --target x86_64-unknown-custom.json -Zbuild-std=core

Current output

rustc successfully compiles, but the output executable is not position-independent:

$ file target/x86_64-unknown-custom/debug/pie
target/x86_64-unknown-custom/debug/pie: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, with debug_info, not stripped

Desired output

A similar error to when a crate type isn't supported e.g.

error: cannot produce position-independent executable for `pie v0.1.0 (/path/to/pie)` as the target `x86_64-unknown-custom` does not support them

Rationale and extra context

No response

Other cases

No response

Anything else?

No response

Start with rustc handling of -Crelocation-model=pie for the supplied custom target spec and reproduce the command with -Zbuild-std=core. Trace where target support is checked or missed, then verify that an unsupported target produces the requested diagnostic instead of a non-position-independent executable.