FS-353: better error reporting for missing lib, don't error on clean

src/mod/languages/mod_yaml/Makefile.am

 include $(top_srcdir)/build/modmake.rulesam
 MODNAME=mod_yaml
 
+if HAVE_YAML
+
 mod_LTLIBRARIES = mod_yaml.la
 mod_yaml_la_SOURCES  = mod_yaml.c
 mod_yaml_la_CFLAGS   = $(AM_CFLAGS)
@@ -8,7 +10,9 @@ mod_yaml_la_CPPFLAGS = $(AM_CPPFLAGS) $(YAML_CFLAGS)
 mod_yaml_la_LIBADD   = $(switch_builddir)/libfreeswitch.la
 mod_yaml_la_LDFLAGS  = -avoid-version -module -no-undefined -shared $(YAML_LIBS)
 
-if HAVE_YAML
 else
-all: $(error You must install libyaml-dev to build mod_yaml)
+install: error
+all: error
+error:
+	$(error You must install libyaml-dev to build mod_yaml)
 endif