Add `dpkg-build-api (= 1)` to the default list of build dependencies

[Tachi107]

Hi!

Commit 0cbf0f0 removed Rules-Requires-Root: no from the default list of build-deps, since this is now the default in trixie. Great!

Still, I think that instead of just removing it, we could do better. The value of Rules-Requires-Root is controlled by the dpkg build API version used by the build, and when unspecified this defaults to v0. Before R-R-R with API v0 switched from binary-targets to no, it would already be set to no under API v1.

Since using API v1 is recommended, but having to remember to add it manually for each package is a bit of a chore, what about adding it to the default set of build-deps, just like debhelper-compat?

You can find more documentation about it in Policy § 5.6.31 and the dpkg-build-api.7 manpage.

Got this idea while writing this review comment: https://salsa.debian.org/go-team/packages/golang-github-gonvenience-idem/-/merge_requests/2#note_638520

[ottok]

Policy:

The default depends on the dpkg-build-api level (see dpkg-build-api(7)). If the dpkg-build-api level is undeclared, it is equivalent to level 0.

API man page:

v1

This is the recommended level. Since dpkg 1.22.0.
Changes from v0 are:

• dpkg-shlibdeps no longer uses the LD_LIBRARY_PATH environment variable. The -l option should be used instead.
• dpkg-buildpackage defaults to Rules-Requires-Root value no. To restore the v0 behavior (from before dpkg 1.22.13) Rules-Requires-Root should be set to binary-targets.
• dpkg-buildpackage expects all required debian/rules targets to be supported and no longer has backwards compatibility fallback code. The required targets are clean, build, build-indep, build-arch, binary-indep and binary-arch.
• vendor.mk defaults to using dpkg_vendor_derives_from_v1 for the dpkg_vendor_derives_from macro. To restore the v0 behavior set dpkg_vendor_derives_from to dpkg_vendor_derives_from_v0.
• default.mk defaults to including buildtools.mk.

Yep, makse sense to do #290.