[PATCH v5 2/4] rust: generate a fatal error if BINDGEN_TARGET is undefined

[Asuna Yang]

From: Asuna Yang <spriteovo at gmail.com>

Generate a friendly fatal error if the target triplet is undefined for
bindgen, rather than having the compiler generate obscure error messages
during the build stage.

This piece of code is copied from `scripts/Makefile.clang`.

Before this commit, error messages might look like:

error: unknown argument: '-mno-riscv-attribute'
error: unsupported argument 'medany' to option '-mcmodel=' for target
'unknown'
error: unsupported option '-march=' for target ''
error: unsupported option '-mno-save-restore' for target ''
error: unknown target triple 'unknown'
panicked at bindgen/ir/context.rs:562:15:
libclang error; possible causes include:
- Invalid flag syntax
- Unrecognized flags
- Invalid flag arguments
- File I/O errors
- Host vs. target architecture mismatch

Acked-by: Miguel Ojeda <ojeda at kernel.org>
Signed-off-by: Asuna Yang <SpriteOvO at gmail.com>
---
 scripts/Makefile.rust | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.rust b/scripts/Makefile.rust
index 5c12b4b8c8b6..b219244cd051 100644
--- a/scripts/Makefile.rust
+++ b/scripts/Makefile.rust
@@ -6,4 +6,8 @@ BINDGEN_TARGET_loongarch	:= loongarch64-linux-gnusf
 BINDGEN_TARGET_um	:= $(BINDGEN_TARGET_$(SUBARCH))
 BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
 
+ifeq ($(BINDGEN_TARGET),)
+$(error add '--target=' option to scripts/Makefile.rust)
+else
 export BINDGEN_TARGET
+endif

-- 
2.51.1