Bug#795510: llvm-toolchain-snapshot FTBFS, apparent version number handling issues.

[peter green]

Package: llvm-toolchain-snapshot
Version: 1:3.7~svn239806-1
Severity: serious

dpkg-buildpackage: host architecture arm64
fakeroot debian/rules clean
dpkg-query: no packages found matching g++-5.2
dpkg: error: --compare-versions takes three arguments: <version> 
<relation> <version>
<--snip many similar errors-->
dpkg-architecture: warning: couldn't determine gcc system type, falling 
back to default (native compilation)
Using gcc:
gcc-5.2 -v
make[1]: gcc-5.2: Command not found
make[1]: *** [override_dh_auto_configure] Error 127

AIUI from gcc/g++ 5 onwards the package names and binary names only use 
the first component of the version numer (where before they used the 
first two components). I belive this is due to a change in versioning 
practices upstream.