Utils: Determine shell from $SHELL instead of hard-coding /bin/sh

Fixes: QTCREATORBUG-24659
Change-Id: Icafc001b681cc76af76b8759a4de84db51146fd4
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/utils/consoleprocess.cpp

@@ -516,7 +516,7 @@ bool ConsoleProcess::start()
                                  " is currently not supported."));
             return false;
         }
-        pcmd = QLatin1String("/bin/sh");
+        pcmd = qEnvironmentVariable("SHELL", "/bin/sh");
         pargs = QtcProcess::Arguments::createUnixArgs(
                         {"-c", (QtcProcess::quoteArg(d->m_commandLine.executable().toString())
                          + ' ' + d->m_commandLine.arguments())});