tests/utils/qmain.cpp: Add missing include for libintl.h

Fixes the following build error under musl libc:

  ../../../tests/utils/qmain.cpp: In function 'int main(int, char**)':
  ../../../tests/utils/qmain.cpp:47:5: error: 'bindtextdomain' was not declared in this scope
     47 |     bindtextdomain(GETTEXT_PACKAGE, LOCALEDIR);
        |     ^~~~~~~~~~~~~~
  ../../../tests/utils/qmain.cpp:48:5: error: 'textdomain' was not declared in this scope
     48 |     textdomain(GETTEXT_PACKAGE);
        |     ^~~~~~~~~~

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/utils/qmain.cpp b/tests/utils/qmain.cpp
index 01a7892..58b1125 100644
--- a/tests/utils/qmain.cpp
+++ b/tests/utils/qmain.cpp
@@ -22,6 +22,7 @@
 #include <QCoreApplication>
 #include <QTimer>
 #include <gtest/gtest.h>
+#include <libintl.h>
 
 #include <libqtdbusmock/DBusMock.h>