Created attachment 465500 [details] build.log Failure during econf, difficult to find a fix for since this is apparently a gentoo specific thing, so third party fixes like the one I found for https://bugs.gentoo.org/show_bug.cgi?id=611172
Created attachment 465502 [details] config.log
Created attachment 465504 [details] emerge --info
checking whether it is possible to resort to fread on /etc/mnttab... no configure: error: could not determine how to read list of mounted file systems these sort of reports really should be sent upstream. you're talking about porting a package to a new OS. in this case, the error is coming from gnulib because findutils uses AC_FUNC_GETMNTENT.
For reference: do not use the winnt prefix profile. Copy the embedded profile into place as mentioned on the mingw wiki and edit it, assuming all you're after is a straight up mingw-w64 toolchain.