The x86_64 wine build gets VKD3D_PE_LIBS with a -L to the x86_64 vkd3d
DLLs. That is right while a separate i386 wine build exists and gets its
own value.

A wow64-only build has no i386 wine build: the x86_64 one builds the i386
PE side as well, and wine takes one VKD3D_PE_LIBS for every PE arch. The
i386 wined3d.dll then links against the x86_64 libvkd3d-1.dll and fails
with "file format not recognized". ld does not skip a mismatched DLL
named with -l:, so listing both directories does not work either.

Under wow64, keep the library names in VKD3D_PE_LIBS and pass each arch
its own directory through i386_LDFLAGS and x86_64_LDFLAGS, which wine's
configure already takes per arch. The i386 vkd3d was only ever built
as a dependency of the i386 wine build, so the x86_64 one now waits for it.

diff --git a/Makefile.in b/Makefile.in
index f8d959c..2ac0b34 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -635,9 +639,23 @@ WINE_aarch64_AUTOCONF_ARGS = \
 WINE_i386_AUTOCONF_ARGS += \
   VKD3D_PE_CFLAGS="-I$(VULKAN_HEADERS_i386_DST)/include -I$(VKD3D_i386_DST)/include/vkd3d" \
   VKD3D_PE_LIBS="-L$(VKD3D_i386_LIBDIR)/vkd3d/i386-windows -l:libvkd3d-1.dll -l:libvkd3d-shader-1.dll -l:libvkd3d-utils-1.dll"
+ifneq ($(findstring i386-unix,$(ARCHS)),)
 WINE_x86_64_AUTOCONF_ARGS += \
   VKD3D_PE_CFLAGS="-I$(VULKAN_HEADERS_x86_64_DST)/include -I$(VKD3D_x86_64_DST)/include/vkd3d" \
   VKD3D_PE_LIBS="-L$(VKD3D_x86_64_LIBDIR)/vkd3d/x86_64-windows -l:libvkd3d-1.dll -l:libvkd3d-shader-1.dll -l:libvkd3d-utils-1.dll"
+else
+# Without i386-unix there is no i386 wine build, and the x86_64 one builds the
+# i386 PE side too (wow64). It links both, but VKD3D_PE_LIBS is one value for
+# every PE arch, so a -L in it would hand the i386 link the x86_64 DLLs. Name
+# the libraries there and give each arch its own directory through its own
+# LDFLAGS instead.
+WINE_x86_64_AUTOCONF_ARGS += \
+  VKD3D_PE_CFLAGS="-I$(VULKAN_HEADERS_x86_64_DST)/include -I$(VKD3D_x86_64_DST)/include/vkd3d" \
+  VKD3D_PE_LIBS="-l:libvkd3d-1.dll -l:libvkd3d-shader-1.dll -l:libvkd3d-utils-1.dll"
+WINE_i386-windows_LIBFLAGS = -L$(VKD3D_i386_LIBDIR)/vkd3d/i386-windows
+WINE_x86_64-windows_LIBFLAGS = -L$(VKD3D_x86_64_LIBDIR)/vkd3d/x86_64-windows
+$(OBJ)/.wine-x86_64-build: $(OBJ)/.vkd3d-i386-post-build
+endif
 
 WINE_DEPENDS = ffmpeg openfst kaldi vosk libxml2 libxkbcommon libpcap
 WINE_i386_DEPENDS = vkd3d