Enable complex retstyle detection on windows as well

I previously thought that the Intel standard for complex return values
on windows was the default for the platform, and so disabled the shims
to work around it. However, it turns out that gfortran uses a consistent
ABI across platforms, and we want to standardize on that, so let's
enable this again. This should fix the memory corruption seen when
calling MKL's `cdotc_64` on `x86_64` Windows.

Author: staticfloat

src/Make.inc

@@ -91,14 +91,11 @@ ifneq (,$(filter $(ARCH), x86_64 i686))
   CBLAS_DIVERGENCE_AUTODETECTION := 1
 endif
 
-# If we're on x86_64 (and NOT on windows), we can do complex return style autodetection
-# We don't do this on Windows because Windows actually prefers arugment retstyle
-ifneq ($(OS),WINNT)
+# If we're on x86_64, we can do complex return style autodetection
 ifneq (,$(filter $(ARCH), x86_64))
   LBT_CFLAGS += -DCOMPLEX_RETSTYLE_AUTODETECTION
   COMPLEX_RETSTYLE_AUTODETECTION := 1
 endif
-endif
 
 
 ifeq ($(VERBOSE),0)

test/direct.jl

@@ -72,10 +72,7 @@ lbt_handle = dlopen("$(lbt_prefix)/$(binlib)/lib$(lbt_link_name).$(shlib_ext)",
     if Sys.ARCH == :x86_64
         @test libs[1].cblas == LBT_CBLAS_CONFORMANT
         if Sys.iswindows()
-            # Technically, this should be "argument", but we disable complex return style
-            # autodetection on windows since the default compilers seem to prefer argument
-            # style, so we'd rather just not touch things on that platform.
-            @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_UNKNOWN
+            @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_ARGUMENT
         else
             @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_NORMAL
         end
@@ -244,11 +241,7 @@ if MKL_jll.is_available() && Sys.ARCH == :x86_64
         @test length(libs) == 1
         @test libs[1].interface == LBT_INTERFACE_ILP64
         @test libs[1].cblas == LBT_CBLAS_DIVERGENT
-        if Sys.iswindows()
-            @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_UNKNOWN
-        else
-            @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_ARGUMENT
-        end
+        @test libs[1].complex_retstyle == LBT_COMPLEX_RETSTYLE_ARGUMENT
 
         # Call cblas_zdotc_sub, asserting that it does not try to call a forwardless-symbol
         empty!(stacktraces)