Debugger: Dumper test GCC version determination

When determining the GCC version we did not use the same environment
that the tests actually use.

As a bonus: an attempt to narrow down UnboundLocalError that occurs
in the QXmlAttributes test in the Win 10 + MinGW + Qt5 test plan
and which I cannot reproduce locally.

Change-Id: Ib12b66091eed7b27871c0bed59d8de019ee2285b
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

share/qtcreator/debugger/gdbbridge.py

@@ -1179,6 +1179,8 @@ class Dumper(DumperBase):
         return self.qtNamespace() + 'Qt::' + enumValue
 
     def lookupNativeType(self, type_name):
+        typeobj = None
+
         if type_name == 'void':
             typeobj = gdb.lookup_type(type_name)
             self.typesToReport[type_name] = typeobj

tests/auto/debugger/tst_dumpers.cpp

@@ -1428,6 +1428,7 @@ void tst_Dumpers::dumper()
     if (data.neededGccVersion.isRestricted && m_debuggerEngine == GdbEngine) {
         QProcess gcc;
         gcc.setWorkingDirectory(t->buildPath);
+        gcc.setProcessEnvironment(m_env);
         gcc.start("gcc", {"--version"});
         QVERIFY(gcc.waitForFinished());
         output = gcc.readAllStandardOutput();