There is no __uid_t defined in musl libc either.

--- src/konfigurator/savehelper.cpp	2014-10-09 09:07:50.000000000 +0200
+++ src/konfigurator/savehelper.cpp	2015-10-09 02:01:04.143074472 +0200
@@ -22,7 +22,7 @@
 #include <kdebug.h>
 #include <unistd.h>
 
-#if defined(Q_CC_MSVC)
+#if defined(Q_CC_MSVC) || !defined(__GLIBC__)
 // TODO: or rather use uid_t in the getuid() call below?
 #define __uid_t uid_t
 #endif
