[3064] Disable building the resover without the flag

Don't build the resolver and its libraries (lib/resolve and lib/libnsas)
in case the --enable-experimental-resolver is not set.

src/bin/resolver/Makefile.am

+if BUILD_EXPERIMENTAL_RESOLVER
+# Build the resolver only with --enable-experimental-resolver
 SUBDIRS = . tests bench
 
 AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
@@ -83,4 +85,4 @@ b10_resolver_LDFLAGS = -pthread
 # and can't use @datadir@ because doesn't expand default ${prefix}
 b10_resolverdir = $(pkgdatadir)
 b10_resolver_DATA = resolver.spec
-
+endif

src/lib/nsas/Makefile.am

+if BUILD_EXPERIMENTAL_RESOLVER
+# Build resolver only with --enable-experimental-resolver
 SUBDIRS = . tests
 
 AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
@@ -61,3 +63,4 @@ EXTRA_DIST = nsas_messages.mes
 
 # Make sure that the generated files are got rid of in a clean operation
 CLEANFILES = *.gcno *.gcda nsas_messages.h nsas_messages.cc
+endif

src/lib/resolve/Makefile.am

+if BUILD_EXPERIMENTAL_RESOLVER
+# Build resolver only with --enable-experimental-resolver
 SUBDIRS = . tests
 
 AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
@@ -47,4 +49,4 @@ if USE_CLANGPP
 libb10_resolve_la_CXXFLAGS += -Wno-error
 endif
 libb10_resolve_la_CPPFLAGS = $(AM_CPPFLAGS)
-
+endif