Aarch64 build of rust-1.39.0 fails

[phodina]

Hi,

I checked the build server and there were no substitutes [1] for rust-1.39.0 
for the Aarch64 system.

When building natively (Pinebook Pro) there is this problem:

$ uname -a
Linux valhalla 5.14.9-gnu #1 SMP PREEMPT 1 aarch64 GNU/Linux
~/guix$ guix build rust -K
...
> /tmp/guix-build-rust-1.39.0.drv-0/mrustc/bin/mrustc 
> rustc-1.39.0-src/src/libcore/lib.rs -o output/libcore.rlib --crate-name core 
> --crate-type rlib -C emit-depfile=output/libcore.rlib.d --crate-tag 0_0_0 -g 
> --cfg debug_assertions -O -L output --edition 2018
rustc-1.39.0-src/src/libcore/slice/mod.rs:67: warn:0:Unexpected attribute 
allow_internal_unstable on associated item
rustc-1.39.0-src/src/libcore/str/mod.rs:2173: warn:0:Unexpected attribute 
allow_internal_unstable on associated item
In file included from output/libcore.rlib.c:7:
output/libcore.rlib.c: In function 
‘ZRQG2ch4core50_0_03ffi10VaListImpl0g2cb05clone5Clone0gb30g’:
output/libcore.rlib.c:219717:10: warning: passing argument 1 of 
‘__builtin_va_copy’ from incompatible pointer type 
[-Wincompatible-pointer-types]
219717 | va_copy(var3, arg0);
| ^~~~
| |
| struct s_ZRG2ch4core50_0_03ffi10VaListImpl0g **
output/libcore.rlib.c:219717:10: note: expected ‘__va_list *’ but argument is 
of type ‘struct s_ZRG2ch4core50_0_03ffi10VaListImpl0g **’
output/libcore.rlib.c:219717:16: error: incompatible type for argument 2 of 
‘__builtin_va_copy’
219717 | va_copy(var3, arg0);
| ^~~~
| |
| struct s_ZRG2ch4core50_0_03ffi10VaListImpl0g *
output/libcore.rlib.c:219717:16: note: expected ‘__va_list’ but argument is of 
type ‘struct s_ZRG2ch4core50_0_03ffi10VaListImpl0g *’
C Compiler failed to execute - error code 256
Process exited with non-zero exit status 1
BUILD FAILED
make: *** [minicargo.mk:82: output/libstd.rlib] Error 1
error: in phase 'build': uncaught exception:
%exception #<&invoke-error program: "make" arguments: ("-f" "minicargo.mk" 
"output/rustc" "-j6" "RUSTC_TARGET=aarch64-unknown-linux-gnu" 
"RUSTC_VERSION=1.39.0" "MRUSTC_TARGET_VER=1.39" "OUTDIR_SUF=") exit-status: 2 
term-signal: #f stop-signal: #f>
phase `build' failed after 1006.4 seconds
command "make" "-f" "minicargo.mk" "output/rustc" "-j6" 
"RUSTC_TARGET=aarch64-unknown-linux-gnu" "RUSTC_VERSION=1.39.0" 
"MRUSTC_TARGET_VER=1.39" "OUTDIR_SUF=" failed with status 2

Not sure if this PR [2] would help as I don't know how to apply the patch to 
the package definition for rust-1.39.

[1] http://ci.guix.gnu.org/search?query=rust-1.39
[2] https://github.com/rust-lang/rust/pull/49878

----
Petr