don't run pkg-config while testing compilation

Author: coke

doc/Language/nativecall.rakudoc

@@ -748,7 +748,7 @@ to be prepended with C<lib> and appended with C<.so> (or just appended with
 C<.dll> on Windows), and will be searched for in the paths in the
 C<LD_LIBRARY_PATH> (C<PATH> on Windows) environment variable.
 
-=begin code
+=begin code :skip-test<runs pkg-config>
 use NativeCall;
 constant LIBMYSQL = 'mysqlclient';
 constant LIBFOO = '/usr/lib/libfoo.so.1';