Makefile, configure: Add option for disabling generation of example certificates

Makefile

@@ -17,7 +17,9 @@ INSTALLEDDATA = $(DATADIR)
 
 all: prosody.install prosodyctl.install prosody.cfg.lua.install prosody.version
 	$(MAKE) -C util-src install
-	$(MAKE) -C certs localhost.crt example.com.crt
+ifeq ($(EXCERTS),yes)
+	$(MAKE) -C certs localhost.crt example.com.crt || true
+endif
 
 install: prosody.install prosodyctl.install prosody.cfg.lua.install util/encodings.so util/encodings.so util/pposix.so util/signal.so
 	install -d $(BIN) $(CONFIG) $(MODULES) $(SOURCE)

configure

@@ -17,6 +17,7 @@ CC=gcc
 CXX=g++
 LD=gcc
 RUNWITH=lua
+EXCERTS=yes
 
 CFLAGS="-fPIC -Wall"
 LDFLAGS="-shared"
@@ -64,6 +65,7 @@ Configure Prosody prior to building.
                             Default is $LD
 --require-config            Will cause Prosody to refuse to run when
                             it fails to find a configuration file
+--no-example-certs          Disables generation of example certificates.
 EOF
 }
 
@@ -178,6 +180,9 @@ do
    --runwith=*)
       RUNWITH="$value"
       ;;
+    --no-example-certs)
+      EXCERTS=
+      ;;
    *)
       echo "Error: Unknown flag: $1"
       exit 1
@@ -349,6 +354,7 @@ CC=$CC
 CXX=$CXX
 LD=$LD
 RUNWITH=$RUNWITH
+EXCERTS=$EXCERTS
 
 EOF