This is an upstream bug which I'm reporting here for completeness.
src/util.c defines `struct timeval t;` around line 76, but does not include <sys/time.h> as required by POSIX . This is okay with glibc (because of how the headers stack), but not with other libcs, like musl. It leads to a compile time error. This is easily fixed with
--- src/util.c.orig 2016-05-27 18:23:49.830943995 +0000
+++ src/utils.c 2016-05-27 18:23:39.534238312 +0000
@@ -21,6 +21,7 @@
#define DEBUG 1
Patch sent upstream at https://bugs.freedesktop.org/show_bug.cgi?id=96268
from what i see on the upstream bug, feel free to apply it to portage tree