kbuild: rust: use `-Zdwarf-version` to support DWARFv5

Rust 1.64.0 introduced (unstable) support for the `-Zdwarf-version`
flag, which allows to select DWARFv5, thus use it.

Link: https://github.com/rust-lang/rust/issues/103057
Link: https://github.com/rust-lang/rust/pull/98350Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240217002602.57270-1-ojeda@kernel.orgSigned-off-by: Miguel Ojeda <ojeda@kernel.org>

scripts/Makefile.debug

@@ -17,6 +17,12 @@ endif
 DEBUG_CFLAGS	+= $(debug-flags-y)
 KBUILD_AFLAGS	+= $(debug-flags-y)
 
+ifdef CONFIG_DEBUG_INFO_DWARF4
+DEBUG_RUSTFLAGS	+= -Zdwarf-version=4
+else ifdef CONFIG_DEBUG_INFO_DWARF5
+DEBUG_RUSTFLAGS	+= -Zdwarf-version=5
+endif
+
 ifdef CONFIG_DEBUG_INFO_REDUCED
 DEBUG_CFLAGS	+= -fno-var-tracking
 DEBUG_RUSTFLAGS	+= -Cdebuginfo=1