Add dev-qt from an older version of the gentoo repo

Qt5 has been removed, we restore it since we still use it.

dev-qt/qt-creator/files/qt-creator-16.0.0-musl-no-execinfo.patch

@@ -0,0 +1,26 @@
+execinfo is unavailable with musl (unless opt to package+use libexecinfo)
+--- a/src/libs/utils/qtcassert.cpp
++++ b/src/libs/utils/qtcassert.cpp
+@@ -9,5 +9,5 @@
+ #include <QTime>
+ 
+-#if defined(Q_OS_UNIX)
++#if defined(Q_OS_UNIX) && defined(__GLIBC__)
+ #include <stdio.h>
+ #include <signal.h>
+@@ -30,5 +30,5 @@
+     if (maxdepth < 0 || maxdepth > ArraySize)
+         maxdepth = ArraySize;
+-#if defined(Q_OS_UNIX)
++#if defined(Q_OS_UNIX) && defined(__GLIBC__)
+     void *bt[ArraySize] = {nullptr};
+     int size = backtrace(bt, maxdepth);
+--- a/src/plugins/qmldesigner/libs/designercore/exceptions/exception.cpp
++++ b/src/plugins/qmldesigner/libs/designercore/exceptions/exception.cpp
+@@ -4,5 +4,5 @@
+ #include "exception.h"
+ 
+-#ifdef Q_OS_LINUX
++#if defined(Q_OS_LINUX) && defined(__GLIBC__)
+ #include <execinfo.h>
+ #include <cxxabi.h>