package/heimdal: add missing dependencies on flex/bison

As host-heimdal is only used by samba4, and samba4 already depends on
host-flex and host-bison, the build issue fixed by this commit is not
directly visible, but can be reproduced by doing "make host-heimdal"
for example in our official Buildroot Docker container:

/home/thomas/projets/buildroot/outputs/foo/build/host-heimdal-f4faaeaba371fff3f8d1bc14389f5e6d70ca8e17/missing: line 81: flex: command not found
WARNING: 'flex' is missing on your system.
         You should only need it if you modified a '.l' file.
         You may want to install the Fast Lexical Analyzer package:
         <https://github.com/westes/flex>
make[4]: *** [Makefile:753: lex.c] Error 127

[...]

updating lex.yylex.c
../../ylwrap: line 176: -d: command not found
make[4]: *** [Makefile:756: parse.c] Error 127

Fix this by adding the missing dependencies.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/heimdal/heimdal.mk

@@ -6,7 +6,7 @@
 
 HEIMDAL_VERSION = f4faaeaba371fff3f8d1bc14389f5e6d70ca8e17
 HEIMDAL_SITE = $(call github,heimdal,heimdal,$(HEIMDAL_VERSION))
-HOST_HEIMDAL_DEPENDENCIES = host-e2fsprogs host-ncurses host-pkgconf host-libxcrypt
+HOST_HEIMDAL_DEPENDENCIES = host-e2fsprogs host-ncurses host-pkgconf host-libxcrypt host-flex host-bison
 HOST_HEIMDAL_AUTORECONF = YES
 HEIMDAL_INSTALL_STAGING = YES
 # static because of -fPIC issues with e2fsprogs on x86_64 host