Trying to build meta-mingw with master of poky and SDKMACHINE = "x86_64-mingw32" I'm calling: bitbake core-image-minimal -c populate_sdk and the build fails in nativesdk-mingw-w64-runtime_3.1.0.bb fails in do_configure with: checking whether we are cross compiling... yes checking for suffix of object files... configure: error: in `/srv/builds/poky/tmp/work/x86_64-nativesdk-mingw32-pokysdk-mingw32/nativesdk-mingw-w64-runtime/3.1.0-r0/build': configure: error: cannot compute suffix of object files: cannot compile
Note: same failure with SDKMACHINE = "i686-mingw32"
I sent out bunch of patches to the mailing lists in October 2016 (not merged) https://lists.yoctoproject.org/pipermail/yocto/2016-October/032306.html which should fix the problem. The comment explicitly says tested with: $ bitbake core-image-minimal -c populate_sdk
I hadn't thought to check the list, especially not so far back. I can confirm those patches resolve this issue.
The needed patches were merged into meta-mingw: http://git.yoctoproject.org/cgit/cgit.cgi/meta-mingw/log/