-$1_$2_CONFIGURE_OPTS += --configure-option=CFLAGS="$$(filter-out -Werror,$$(SRC_CC_OPTS)) $$($1_CC_OPTS) $$($1_$2_CC_OPTS)"
-$1_$2_CONFIGURE_OPTS += --configure-option=LDFLAGS="$$(SRC_LD_OPTS) $$($1_LD_OPTS) $$($1_$2_LD_OPTS)"
+$1_$2_CONFIGURE_OPTS += --configure-option=CFLAGS="$$(filter-out -Werror,$$(SRC_CC_OPTS)) $$(CONF_CC_OPTS_STAGE$3) $$($1_CC_OPTS) $$($1_$2_CC_OPTS)"
+$1_$2_CONFIGURE_OPTS += --configure-option=LDFLAGS="$$(SRC_LD_OPTS) $$(CONF_LD_OPTS_STAGE$3) $$($1_LD_OPTS) $$($1_$2_LD_OPTS)"
+$1_$2_CONFIGURE_OPTS += --configure-option=CPPFLAGS="$$(SRC_CPP_OPTS) $$(CONF_CPP_OPTS_STAGE$3) $$($1_CPP_OPTS) $$($1_$2_CPP_OPTS)"
+
+ifneq "$$(ICONV_INCLUDE_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-iconv-includes="$$(ICONV_INCLUDE_DIRS)"
+endif
+
+ifneq "$$(ICONV_LIB_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-iconv-libraries="$$(ICONV_LIB_DIRS)"
+endif
+
+ifneq "$$(GMP_INCLUDE_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-gmp-includes="$$(GMP_INCLUDE_DIRS)"
+endif
+
+ifneq "$$(GMP_LIB_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-gmp-libraries="$$(GMP_LIB_DIRS)"
+endif
+
+ifeq "$3" "0"
+$1_$2_CONFIGURE_OPTS += $$(BOOT_PKG_CONSTRAINTS)
+endif