bind: support compile-time exclusion of DNS-over-HTTPS support

DoH is enabled by default, but disabling it removes the need to link
against libnghttp2, which may be desirable more constrained
environments.

Signed-off-by: Noah Meyerhans <frodo@morgul.net>

net/bind/Config.in

@@ -20,3 +20,17 @@ config BIND_LIBXML2
 		format. Building with libjson support will require the
 		libxml2 package to be installed as well.
 endif
+
+if PACKAGE_bind-libs
+
+config BIND_ENABLE_DOH
+	bool
+	default y
+	prompt "Include DNS-over-HTTPS support in bind"
+	help
+		BIND 9 supports DNS-over-HTTPS and enables it by
+		default.  This requires linking against libnghttp2.
+		You can disable DoHTTPS if you do not need it or need
+		to avoid the additional library dependency.
+
+endif

net/bind/Makefile

@@ -31,11 +31,10 @@ PKG_INSTALL:=1
 PKG_USE_MIPS16:=0
 PKG_BUILD_PARALLEL:=1
 
-PKG_BUILD_DEPENDS:=nghttp2
-
 PKG_CONFIG_DEPENDS := \
 	CONFIG_BIND_LIBJSON \
-	CONFIG_BIND_LIBXML2
+	CONFIG_BIND_LIBXML2 \
+	CONFIG_BIND_ENABLE_DOH
 
 PKG_BUILD_DEPENDS += BIND_LIBXML2:libxml2 BIND_LIBJSON:libjson-c
 
@@ -59,7 +58,7 @@ define Package/bind-libs
 	+libpthread \
 	+libatomic \
 	+libuv \
-	+libnghttp2 \
+	+BIND_ENABLE_DOH:libnghttp2 \
 	+BIND_LIBXML2:libxml2 \
 	+BIND_LIBJSON:libjson-c
   TITLE:=bind shared libraries
@@ -162,6 +161,14 @@ else
 		--with-libxml2=no
 endif
 
+ifdef CONFIG_BIND_ENABLE_DOH
+	CONFIGURE_ARGS += \
+		--enable-doh
+else
+	CONFIGURE_ARGS += \
+		--disable-doh
+endif
+
 CONFIGURE_VARS += \
 	BUILD_CC="$(TARGET_CC)" \