package/strongswan: add botan optional dependency

botan is an optional dependency since version 5.7.0 and
https://github.com/strongswan/strongswan/commit/af26cc4d8542fb6aaea9bfc5aaae1b139faee94a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/strongswan/Config.in

@@ -31,6 +31,23 @@ choice
 	prompt "Cryptographic backend"
 	default BR2_PACKAGE_STRONGSWAN_GMP
 
+config BR2_PACKAGE_STRONGSWAN_BOTAN
+	bool "botan"
+	depends on BR2_PACKAGE_BOTAN_ARCH_SUPPORTS
+	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_64735
+	select BR2_PACKAGE_BOTAN
+
+comment "botan backend needs a toolchain w/ C++, gcc >= 4.8"
+	depends on !BR2_INSTALL_LIBSTDCPP \
+		|| !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+	depends on BR2_PACKAGE_BOTAN_ARCH_SUPPORTS
+
+comment "botan backend needs a toolchain not affected by GCC bug 64735"
+	depends on BR2_PACKAGE_BOTAN_ARCH_SUPPORTS
+	depends on BR2_TOOLCHAIN_HAS_GCC_BUG_64735
+
 config BR2_PACKAGE_STRONGSWAN_OPENSSL
 	bool "OpenSSL"
 	select BR2_PACKAGE_OPENSSL

package/strongswan/strongswan.mk

@@ -18,6 +18,7 @@ STRONGSWAN_CONF_OPTS += \
 	--enable-pkcs11=yes \
 	--enable-kernel-netlink=yes \
 	--enable-socket-default=yes \
+	--enable-botan=$(if $(BR2_PACKAGE_STRONGSWAN_BOTAN),yes,no) \
 	--enable-openssl=$(if $(BR2_PACKAGE_STRONGSWAN_OPENSSL),yes,no) \
 	--enable-gcrypt=$(if $(BR2_PACKAGE_STRONGSWAN_GCRYPT),yes,no) \
 	--enable-gmp=$(if $(BR2_PACKAGE_STRONGSWAN_GMP),yes,no) \
@@ -66,6 +67,7 @@ STRONGSWAN_CONF_ENV += LIBS='-latomic'
 endif
 
 STRONGSWAN_DEPENDENCIES += \
+	$(if $(BR2_PACKAGE_STRONGSWAN_BOTAN),botan) \
 	$(if $(BR2_PACKAGE_STRONGSWAN_OPENSSL),openssl) \
 	$(if $(BR2_PACKAGE_STRONGSWAN_GCRYPT),libgcrypt) \
 	$(if $(BR2_PACKAGE_STRONGSWAN_GMP),gmp) \