linux-source: Recommend bison and flex, always needed to build the kernel

debian/changelog

@@ -805,6 +805,7 @@ linux (4.19.34-1) UNRELEASED; urgency=medium
   * [sparc64] linux-image: Recommend grub-ieee1275 instead of (removed) silo
   * [powerpc,ppc64,ppc64el] linux-image: Recommend grub-ieee1275
   * [i386] Add grub-efi-ia32 as an alternate recommended bootloader
+  * linux-source: Recommend bison and flex, always needed to build the kernel
 
   [ YunQiang Su ]
   * [mips*r6] Re-enable CONFIG_JUMP_LABEL, which has been fixed in upstream.

debian/templates/control.sourcebin.in

@@ -4,7 +4,7 @@ Architecture: all
 Section: kernel
 Build-Depends: patchutils
 Depends: binutils, xz-utils, ${misc:Depends}
-Recommends: libc6-dev | libc-dev, gcc, make, bc, @source_basename@-config-@version@
+Recommends: libc6-dev | libc-dev, gcc, make, bc, bison, flex, @source_basename@-config-@version@
 Suggests: libncurses-dev | ncurses-dev, libqt4-dev, pkg-config
 Multi-Arch: foreign
 Description: Linux kernel source for version @version@ with Debian patches