samba: predefine a autoconf result for enums with negative values

The configure script tries to find out if enums can be negative, this is not
supported when cross compiling, since it tries to run the binary. This commit
sets the test to yes, i.e. negative enums are possible.

package/samba/samba.mk

@@ -33,6 +33,7 @@ $(SAMBA_DIR)/.configured: $(SAMBA_DIR)/.unpacked
 		samba_cv_HAVE_FCNTL_LOCK=yes \
 		samba_cv_HAVE_SECURE_MKSTEMP=yes \
 		samba_cv_fpie=no \
+		SMB_BUILD_CC_NEGATIVE_ENUM_VALUES=yes \
 		./configure \
 		--target=$(GNU_TARGET_NAME) \
 		--host=$(GNU_TARGET_NAME) \