make: source build ignores debug in DEB_BUILD_OPTIONS

[Philip Ashmore]

Binary package hint: make

After
    $ sudo apt-get build-dep make
    $ apt-get source make
    $ cd make-dfsg-3.81
    $ DEB_BUILD_OPTIONS="debug nostrip noopt" logsave ../make-debug.log dpkg-buildpackage -uc -us -rfakeroot

I noticed that the source files were being built with "-O2" instead of "-O0".
A comparison with the "remake" package (which behaves as expected) revealed that the environment setting made by dpkg-buildpackage was being stepped on by debian/common/copt.mk

I created a patch as per
https://wiki.ubuntu.com/PackagingGuide/Howtos/PatchingWithoutPatchSystem?highlight=(CategoryPackagingGuide)

and have tested it locally - debugging builds work as expected - please find the patch attached.

Unfortunately make must first be converted to use dpatch before this patch can be incorporated into the distribution.
"remake" uses dpatch and supplying a "dpatch" patch is all that's required with that package.