bdwgc: add optional cplusplus support

Use CFLAGS_EXTRA to pass C and C++ flags in a single variable

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/bdwgc/bdwgc.mk

@@ -19,17 +19,23 @@ HOST_BDWGC_DEPENDENCIES = host-libatomic_ops host-pkgconf
 # solution.
 BDWGC_AUTORECONF = YES
 
-BDWGC_CFLAGS = $(TARGET_CFLAGS)
+BDWGC_CONF_OPTS = CFLAGS_EXTRA="$(BDWGC_CFLAGS_EXTRA)"
 ifeq ($(BR2_sparc),y)
-BDWGC_CFLAGS += -DAO_NO_SPARC_V9
+BDWGC_CFLAGS_EXTRA += -DAO_NO_SPARC_V9
 endif
 ifeq ($(BR2_STATIC_LIBS),y)
-BDWGC_CFLAGS += -DGC_NO_DLOPEN
+BDWGC_CFLAGS_EXTRA += -DGC_NO_DLOPEN
 endif
 
 # Ensure we use the system libatomic_ops, and not the internal one.
-BDWGC_CONF_OPTS = --with-libatomic-ops=yes CFLAGS="$(BDWGC_CFLAGS)"
+BDWGC_CONF_OPTS += --with-libatomic-ops=yes
 HOST_BDWGC_CONF_OPTS = --with-libatomic-ops=yes
 
+ifeq ($(BR2_INSTALL_LIBSTDCPP),y)
+BDWGC_CONF_OPTS += --enable-cplusplus
+else
+BDWGC_CONF_OPTS += --disable-cplusplus
+endif
+
 $(eval $(autotools-package))
 $(eval $(host-autotools-package))