(Sorry for the spam.)

Figure one thing out: removing mingw from the inputs solves the gcc
vs. winegcc issue.

Now dxvk fails to compile with the following error:


--8<---------------cut here---------------start------------->8---
starting phase `build'
[1/189] Generating version.h with a custom command.
[2/189] Compiling C++ object 'src/util/ed6d25d@@util@sta/util_env.cpp.o'.
FAILED: src/util/ed6d25d@@util@sta/util_env.cpp.o 
wineg++ -Isrc/util/ed6d25d@@util@sta -Isrc/util -I../source/src/util -I../source/./include -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -std=c++1z -DNOMINMAX -fPIC -m64 --no-gnu-unique -MD -MQ 'src/util/ed6d25d@@util@sta/util_env.cpp.o' -MF 'src/util/ed6d25d@@util@sta/util_env.cpp.o.d' -o 'src/util/ed6d25d@@util@sta/util_env.cpp.o' -c ../source/src/util/util_env.cpp
In file included from ../source/src/util/util_env.h:3:0,
                 from ../source/src/util/util_env.cpp:1:
../source/src/util/util_string.h:9:15: error: expected ‘{’ before ‘::’ token
 namespace dxvk::str {
               ^
../source/src/util/util_string.h:9:17: error: ‘str’ in namespace ‘::’ does not name a type
 namespace dxvk::str {
                 ^
In file included from ../source/src/util/util_env.cpp:1:0:
../source/src/util/util_env.h:5:15: error: expected ‘{’ before ‘::’ token
 namespace dxvk::env {
               ^
../source/src/util/util_env.h:5:17: error: ‘env’ in namespace ‘::’ does not name a type
 namespace dxvk::env {
                 ^
../source/src/util/util_env.cpp:5:15: error: expected ‘{’ before ‘::’ token
 namespace dxvk::env {
               ^
../source/src/util/util_env.cpp:5:17: error: ‘env’ in namespace ‘::’ does not name a type
 namespace dxvk::env {
                 ^
../source/src/util/util_env.cpp:54:1: error: expected ‘}’ at end of input
 }
 ^
../source/src/util/util_env.cpp:54:1: error: expected ‘}’ at end of input
../source/src/util/util_env.cpp:54:1: error: expected ‘}’ at end of input
winegcc: g++ failed
ninja: build stopped: subcommand failed.
Backtrace:
           4 (primitive-load "/gnu/store/wnn0w163nxrr3v48y0d1pwpsfxj…")
In ice-9/eval.scm:
   191:35  3 (_ _)
In srfi/srfi-1.scm:
   863:16  2 (every1 #<procedure 5365c0 at /gnu/store/073micbrwvihh…> …)
In /gnu/store/073micbrwvihh46kj1b607xjgjyfxv2f-module-import/guix/build/gnu-build-system.scm:
   799:28  1 (_ _)
In /gnu/store/073micbrwvihh46kj1b607xjgjyfxv2f-module-import/guix/build/utils.scm:
    616:6  0 (invoke _ . _)

/gnu/store/073micbrwvihh46kj1b607xjgjyfxv2f-module-import/guix/build/utils.scm:616:6: In procedure invoke:
Throw to key `srfi-34' with args `(#<condition &invoke-error [program: "ninja" arguments: ("-j" "1") exit-status: 1 term-signal: #f stop-signal: #f] 491d40>)'.
note: keeping build directory `/tmp/guix-build-dxvk-1.0.1.drv-11'

--8<---------------cut here---------------end--------------->8---

Looks like it does not understand C++ :p

-- 
Pierre Neidhardt
https://ambrevar.xyz/