Fix incorrect uname usage.

The POSIX function uname() can return any non-negative value for success.
- Example: Solaris 10 returns 1 on success.
See: http://pubs.opengroup.org/onlinepubs/009695399/functions/uname.html

Change-Id: Ic3d51f94a31d8b562b28a2d09df3d31b04c77dc8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
(cherry picked from qtbase/e97c37a37ac27f9ab901e974f0a882e81ffd571d)
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/shared/proparser/qmakeevaluator.cpp

@@ -1026,7 +1026,7 @@ void QMakeEvaluator::loadDefaults()
 # endif
 #elif defined(Q_OS_UNIX)
     struct utsname name;
-    if (!uname(&name)) {
+    if (uname(&name) != -1) {
         vars[ProKey("QMAKE_HOST.os")] << ProString(name.sysname);
         vars[ProKey("QMAKE_HOST.name")] << ProString(QString::fromLocal8Bit(name.nodename));
         vars[ProKey("QMAKE_HOST.version")] << ProString(name.release);