Skip test cases/frameworks/19 pcap if pcap not found

test cases/frameworks/19 pcap/meson.build

@@ -1,6 +1,10 @@
 project('pcap test', 'c')
 
-pcap_dep = dependency('pcap', version : '>=1.0')
+pcap_dep = dependency('pcap', version : '>=1.0', required: false)
+
+if not pcap_dep.found()
+  error('MESON_SKIP_TEST pcap not found.')
+endif
 
 pcap_ver = pcap_dep.version()
 assert(pcap_ver.split('.').length() > 1, 'pcap version is "@0@"'.format(pcap_ver))
@@ -9,6 +13,6 @@ e = executable('pcap_prog', 'pcap_prog.c', dependencies : pcap_dep)
 
 test('pcaptest', e)
 
-# Ensure discovery bia the configuration tools work also
+# Ensure discovery via the configuration tools work also
 pcap_dep = dependency('pcap', version : '>=1.0', method : 'pcap-config')
 pcap_dep = dependency('pcap', version : '>=1.0', method : 'config-tool')