Bug#823280: invalid Build-Depends with DEB_BUILD_OPTIONS=nolang=biarch

[Helmut Grohne <helmut@subdivi.de>]

Package: gcc-5,gcc-6
Severity: wishlist
Tags: patch
User: helmutg@debian.org
Usertags: rebootstrap

Hi Matthias,

Starting with dpkg 1.18.5, the parsing of Build-Depends has become
stricter. This causes dpkg-shlibdeps to error out on gcc's Build-Depends
when disabling multilib with DEB_BUILD_OPTIONS=nolang=biarch.

    dpkg-shlibdeps: warning: can't parse dependency g++-multilib [] <!cross>

The cause here is that the make variable $(multilib_archs) ends up being
empty resulting in an empty arch restriction. This results in a build
failure even for native builds. My proposed patch skips this dependency
entirely when multilib is disabled. It may make sense to turn this
option into a build profile though.

Helmut

--- a/debian/rules.conf
+++ b/debian/rules.conf
@@ -363,7 +363,9 @@
 
 # needed for the include/asm symlink to run the testsuite for
 # non default multilibs
+ifneq ($(multilib_archs),)
-GCC_MULTILIB_BUILD_DEP = g++-multilib [$(multilib_archs)]$(pf_ncross),
+GCC_MULTILIB_BUILD_DEP += g++-multilib [$(multilib_archs)]$(pf_ncross),
+endif
 GCC_MULTILIB_BUILD_DEP += g++-5 [arm64]$(pf_ncross),

 LIBUNWIND_DEV_DEP := libunwind7-dev$(LS)$(AQ) (>= 0.98.5-6)