McuSupport: Enable and preselect usage of the shipped JOM (on Windows)

- Set CMake generator to "NMake Makefiles JOM"
- Add ICore::libexecPath to environment path
- Set the environment for the run configuration

Change-Id: Ie7b2dc1513b366911b429d77cc4a1954be531075
Reviewed-by: Aurindam Jana <aurindam.jana@qt.io>

src/plugins/mcusupport/mcusupportrunconfiguration.cpp

@@ -94,6 +94,7 @@ public:
             r.workingDirectory =
                     target->activeBuildConfiguration()->buildDirectory().toUserOutput();
             r.setCommandLine(cmd);
+            r.environment = target->activeBuildConfiguration()->environment();
             SimpleTargetRunner::doStart(r, {});
         });
     }