multiple definition of 'main' when targeting mingw


I've just had a report from a user that building this code:

int main()

with Clang, targeting 64-bit mingw, fails with:

.../Temp/x2-767132.o:fake:(.text+0x0): multiple definition of `main'
...\Temp\ccyBrUu0.o:x.cpp:(.text+0x0): first defined here

Apparently this has been broken on trunk for ~3 days. Can anyone
reproduce this? Anyone know what's wrong here, or where this "fake"
source file came from?