This is a backport of a trivial fix thats in 2.3.2 but not in 2.3.1 in the file byteswap.h. Basically, a few internal glibc functions __bswap_32 and __bswap_16 don't get defined for non-GCC compilers, and so some compiles fail (QT) with them. If there is another 2.3.1 based release it would be nice to get this in, but it's non-critical.
Created attachment 11924 [details, diff] diff between 2.3.1's byteswap.h and 2.3.2's byteswap.h
Created attachment 11925 [details, diff] diff between the glibc-2.3.1-r4.ebuild and my glibc-2.3.1-r5.ebuild which includes the above patch. (trivial)
glibc-2.3.2-r1 is stable on most archs by now (maybe not arm), so this issue should be moot by now. Resolving as FIXED.