platform: fix build

  ./src/libnm-platform/nm-platform.h:1315: undefined reference to `_nm_utils_ip4_prefix_to_netmask'
  make[2]: *** [Makefile:11063: src/core/platform/tests/test-cleanup-fake] Error 1
  ./src/libnm-platform/nm-platform.h:1315: undefined reference to `_nm_utils_ip4_prefix_to_netmask'
  make[2]: *** [Makefile:11070: src/core/platform/tests/test-cleanup-linux] Error 1

src/libnm-platform/nm-platform.h

@@ -8,6 +8,7 @@
 
 #include "libnm-platform/nmp-base.h"
 #include "libnm-base/nm-base.h"
+#include "libnm-glib-aux/nm-shared-utils.h"
 
 #define NM_TYPE_PLATFORM (nm_platform_get_type())
 #define NM_PLATFORM(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj), NM_TYPE_PLATFORM, NMPlatform))

[NetworkManagerCI]

https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/3449/

Result: STABLE: All tests passing

Passed: 1198, Failed: 0, Skipped: 48

[NetworkManagerCI]

https://jenkins-networkmanager.apps.ocp.ci.centos.org/job/NetworkManager-code-mr/1086/

Result: STABLE: All tests passed!

M0 PASS: Passed: 592, Failed: 0, Skipped: 30

M1 PASS: Passed: 587, Failed: 0, Skipped: 36

Passed: 1179, Failed 0, Skipped 66.

Executed on: CentOS 8-stream