package/bind: fix build failure due to gcc bug 101737

The bind package exhibits gcc bug 101737 when built for the SH4
architecture with optimization enabled, which causes a build failure.

As done for other packages in Buildroot work around this gcc bug by
setting optimization to -O0 if BR2_TOOLCHAIN_HAS_GCC_BUG_101737=y.
To achieve this we need to correct the override of CFLAGS by using:
BIND_CONF_OPTS += CFLAGS="$(BIND_CFLAGS)"
instead of:
BIND_CONF_ENV = BUILD_CFLAGS"$(BIND_CFLAGS)"
since the latter doesn't work as expected and doesn't override CFLAGS.

Fixes:
http://autobuild.buildroot.net/results/e7b/e7b9a4cbee8bb16431609182b96d1ac1ccec10e7/

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 105e3b34be2e51e03721710fb3e91aa93083b1ce)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/bind/bind.mk

@@ -28,7 +28,6 @@ BIND_TARGET_SERVER_SBIN += dnssec-keyfromlabel dnssec-signzone tsig-keygen
 BIND_TARGET_TOOLS_BIN = dig host nslookup nsupdate
 BIND_CONF_ENV = \
 	BUILD_CC="$(TARGET_CC)" \
-	BUILD_CFLAGS="$(TARGET_CFLAGS)" \
 	LIBS=`$(PKG_CONFIG_HOST_BINARY) --libs openssl`
 BIND_CONF_OPTS = \
 	--without-cmocka \
@@ -39,6 +38,14 @@ BIND_CONF_OPTS = \
 
 BIND_DEPENDENCIES = host-pkgconf libuv openssl
 
+BIND_CFLAGS = $(TARGET_CFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_101737),y)
+BIND_CFLAGS += -O0
+endif
+
+BIND_CONF_OPTS += CFLAGS="$(BIND_CFLAGS)"
+
 ifeq ($(BR2_PACKAGE_ZLIB),y)
 BIND_CONF_OPTS += --with-zlib
 BIND_DEPENDENCIES += zlib