I'm running into this COM related issue with some Windows
headers, in the case when each GUID is declared in such a file as
follows.
```C
EXTERN_GUID(IID_IBlahBlahBlah, 0xabcdef12, 0x11d2, 0xab3a, 0xc0,
0x4f, [...] );
```
and ImportC which is compiling `blah.c` containing only a few
macro
I found a way to make a solution for 64 bit Windows mechanically
with many MSVC intrinsics, using only mingw64.
Here's an [MSYS2](https://www.msys2.org/) bash script.
```bash
gcc -E -P intrin.c -o vcintrinsics.c
sed -i 's/extern __inline__
__attribute__((__always_inline__,__gnu_inline__))//g'
Is it me, or does the [DFLAGS environment
variable](https://dlang.org/dmd-windows.html#environment) have no
effect on DMD.
```
dmd --version
DMD64 D Compiler v2.107.0
```
