Building the latest master GCC using msys2.

[peter0x44 <peter0x44@disroot.org>]

Hi all,

I was trying to build the latest trunk gcc, using msys2, and I did it 
likeso:
I installed msys2, and then used `pacman -S base-devel` and `pacman -S 
mingw-w64-ucrt-x86_64-gcc`
I downloaded the gcc source and extracted it.

Here's my configure command:


../gcc-master/configure --host=x86_64-w64-mingw32 --enable-languages=c 
--disable-multilib --disable-bootstrap --with-sysroot=/ucrt64 
--enable-lto

the configure goes fine, but when I go to build, I get the following 
error mid-way through:
The directory (BUILD_SYSTEM_HEADER_DIR) that should contain system 
headers does not exist:
   /ucrt64/mingw/include

I tried without passing any sysroot, and with --sysroot=/mingw64.
There appears to be no directory named "mingw" present on the root.
There is only "mingw64", "mingw32", "ucrt64", etc.

Does anyone know what I'm doing wrong? Is there something I don't 
understand about the purpose of --with-sysroot?

Thanks,
Peter D.